ALUMINIUM ALLOY AND METHOD FOR PRODUCING THE ALLOY

Abstract

A rapidly-solidified and plastically consolidated aluminium alloy comprises between 3.00 and 10.00 wt. % of magnesium and between 1.00 and 6.00 wt. % of manganese and dispersoid forming transition elements that are selected from the group consisting of chromium, vanadium, titanium, zirconium, molybdenum, cobalt and niobium. The total amount of these transition elements is at least 0.50 wt. %. The maximum amounts of these elements is 1.50 wt. % for Cr, 1.50 wt. % for V, 1.00 wt. % for Ti, 1.00 wt. % for Zr, 1.50 wt. % for Mo, 1.50 wt. % for Co and 1.00 wt. % for Nb. The aluminium alloy is corrosion resistant and allows, due to its fine grained stabilized structure, to combine a high yield strength at room temperature with a good thermal resistance and with relatively low forming forces at high temperatures. The liquidus temperature of the alloy remains relatively low so that it can be produced easily on an industrial scale.

Claims

1. An aluminium alloy which is rapidly solidified and plastically consolidated and which comprises aluminium (Al) and: between 3.00 and 10.00 wt. % of magnesium (Mg); more than 1.00 and less than 6.00 wt. % of manganese (Mn); and one or more transition elements which are selected from the group consisting of chromium (Cr), vanadium (V), titanium (Ti), zirconium (Zr), molybdenum (Mo), cobalt (Co) and niobium (Nb), a total amount of the one or more transition elements being at least equal to 0.50 wt. % and the maximum amounts of the transition elements being 1.50 wt. % for Cr, 1.50 wt. % for V, 1.00 wt. % for Ti, 1.00 wt. % for Zr, 1.50 wt. % for Mo, 1.50 wt. % for Co and 1.00 wt. % for Nb, wherein the aluminium alloy comprises: no or less than 2.00 wt. %, preferably less than 1.00 wt. % of zinc (Zn), no or less than 2.00 wt. %, preferably less than 1.00 wt. % of silicon (Si), no or less than 1.00 wt. % of scandium (Sc) and no or less than 1.00 wt. % of tungsten (W); no other elements different from Al, Mg, Mn, Cr, V, Ti, Zr, Mo, Co, Nb, Zn, Si, Sc and W or in total less than 4.00 wt. %, preferably less than 2.0 wt. % and more preferably less than 1.00 wt. % of the other elements; and aluminium as balance.

2. The aluminium alloy according to claim 1, which comprises at most 1.20 wt. %, preferably at most 1.00 wt. % and more preferably at most 0.75 wt. % of V.

3. The aluminium alloy according to claim 1, which comprises at most 1.40 wt. %, preferably at most 1.30 wt. % and more preferably at most 1.20 wt. % of Cr.

4. The aluminium alloy according to claim 1, which comprises at least 0.10 wt. %, preferably at least 0.20 wt. %, more preferably at least 0.30 wt. % and most preferably at least 0.40 wt. % of Cr.

5. The aluminium alloy according to claim 1, which comprises at least 0.10 wt. %, preferably at least 0.20 wt. %, more preferably at least 0.30 wt. % and most preferably at least 0.40 wt. % of V.

6. The aluminium alloy according to claim 1, which comprises two or more, preferably three or more of the transition elements.

7. The aluminium alloy according to claim 1, which comprises Cr and V in a total amount of at least 0.50 wt. %, preferably of at least 0.70 wt. % and more preferably of at least 0.90 wt. %.

8. The aluminium alloy according to claim 1, which comprises Cr and/or V, and additionally at least 0.15 wt. %, preferably at least 0.20 wt. % of Ti, at least 0.15 wt. %, preferably at least 0.20 wt. % of Zr, at least 0.15 wt. %, preferably at least 0.20 wt. % of Mo, at least 0.15 wt. %, preferably at least 0.20 wt. % of Co and/or at least 0.15 wt. %, preferably at least 0.20 wt. % of Nb.

9. The aluminium alloy according to claim 1, wherein the total amount of the one or more transition elements is larger than 0.70 wt. %, preferably larger than 0.80 wt. %, more preferably larger than 0.90 wt. % and most preferably larger than 1.00 wt. %.

10. The aluminium alloy according to claim 1, wherein the total amount of the one or more transition elements is smaller than 3.00 wt. %, preferably smaller than 2.75 wt. %, more preferably smaller than 2.50 wt. % and most preferably smaller than 2.25 wt. %.

11. The aluminium alloy according to claim 1, which comprises at least 1.10 wt. %, preferably at least 1.20 wt. %, more preferably at least 1.30 wt. % and most preferably at least 1.40 wt. % of Mn.

12. The aluminium alloy according to claim 1, which comprises less than 5.00 wt. %, preferably less than 4.50 wt. % and more preferably less than 4.00 wt. % of Mn.

13. The aluminium alloy according to claim 1, which comprises at least 4.00 wt. %, preferably at least 4.50 wt. %, more preferably at least 5.00 wt. %, most preferably at least 5.50 wt. % and even more preferably at least 6.00 wt. % of Mg.

14. The aluminium alloy according to claim 1, which comprises less than 9.00 wt. %, preferably less than 8.00 wt. % and more preferably less than 7.00 wt. % of Mg.

15. The aluminium alloy according to claim 1, which has a true yield strength (YS, R.sub.0.2), measured at 20 C. in accordance with ASTM E8/E8M-13a, of at least 400 MPa, preferably of at least 450 MPa, more preferably of at least 500 MPa and most preferably of at least 550 MPa.

16. The aluminium alloy according to claim 1, which has a maximum true stress during plastic deformation in a compression test at a true strain rate of 10.sup.2 per second, of less than 25 MPa, preferably less than 21 MPa and more preferably less than 18 MPa at 450 C., and/or of less than 20 MPa, preferably less than 17 MPa and more preferably less than 14 MPa at 500 C., and/or of less than 17 MPa, preferably less than 14 MPa and more preferably less than 8 MPa at 550 C.

17. The aluminium alloy according to claim 1, which has a true yield strength (YS, R.sub.0.2), measured at 20 C. in accordance with ASTM E8/E8M-13a, and a maximum true stress during plastic deformation in a compression test to 50% of an initial height at a temperature of 525 C. and at a true strain rate of 10.sup.2 per second, which maximum true stress, expressed in MPa, is smaller than 3.0%, preferably smaller than 2.0% and more preferably smaller than 1.5% of the true yield strength expressed in MPa.

18. The aluminium alloy according to claim 1, which comprises between 1.50 and 3.50 wt. %, preferably between 2.00 and 3.00 wt. % of Mn and between 3.00 and 5.00 wt. %, preferably between 3.00 and 4.50 wt. % of Mg, with the total amount of the one or more transition elements being less than 1.00 wt. %, and with Cr being preferably either absent or present in an amount of at most 0.3 wt. % or preferably of at most 0.2 wt. %.

19. The aluminium alloy according to claim 18, which has a percent elongation at fracture (el) of at least 15%, preferably of at least 18%, and a true yield strength (YS, R.sub.0.2), of at least 320 MPa, preferably of at least 340 MPa, both measured at 20 C. in accordance with ASTM E8/E8M-13a, the true yield strength being preferably further defined by the following equation:
YS>525-10.el(equation 1)

20. The aluminium alloy according to claim 1, which comprises no or less than 3.00 wt. % of Fe, preferably no or less than 2.00 wt. % of Fe, and more preferably no or less than 1.00% of Fe, and no or less than 2.00 wt. % of Cu, preferably no or less than 1.00 wt. % of Cu, and no or less than 0.40 wt. % of Ni, preferably no or less than 0.30 wt. % of Ni, and no or less than 0.40 wt. % of Bi, preferably no or less than 0.30 wt. % of Bi, and no or less than 0.40 wt. % of Sn, preferably no or less than 0.30 wt. % of Sn, and no or less than 0.40 wt. % of Pb, preferably no or less than 0.30 wt. % of Pb.

21. The aluminium alloy according to claim 1, which has a liquidus temperature lower than 950 C., preferably lower than 900 C. and more preferably lower than 850 C.

22. The aluminium alloy according to claim 1, which has, as plastically consolidated, an average grain size, measured in accordance with standard ASTM E2627-13 (2019), of less than 2000 nm, preferably of less than 1000 nm, more preferably of less than 800 nm and most preferably of less than 600 nm.

23. The aluminium alloy according to claim 1, which is hot forged, in particular die forged, and which has an average grain size, measured in accordance with standard ASTM E2627-13 (2019), of less than 4000 nm, preferably of less than 2000 nm, more preferably of less than 1500 nm and most preferably of less than 1200 nm.

24. The aluminium alloy according to claim 1, which is substantially free of primary intermetallic phases and preferably also of dendrites.

25. A method for producing an aluminium alloy according to claim 1, which aluminium alloy has a liquidus and a solidus temperature and a predetermined difference between the liquidus and the solidus temperature, in which method a molten aluminium alloy composition is made having a composition as defined in any one of the claims 1 to 24, wherein the molten aluminium alloy composition is rapidly solidified in a form of pieces of rapidly solidified material, and wherein the pieces of the rapidly solidified material are plastically consolidated to produce the plastically consolidated aluminium alloy.

26. The method according to claim 25, wherein the liquidus temperature is lower than 950 C., preferably lower than 900 C. and more preferably lower than 850 C.

27. The method according to claim 25, wherein the molten aluminium alloy composition is ejected from at least one nozzle to be rapidly solidified, the molten aluminium alloy composition exiting the at least one nozzle having a predetermined temperature upon exiting the at least one nozzle and is rapidly solidified by being cooled down within a predetermined period of time to the solidus temperature of the aluminium alloy at an average cooling rate which is determined as a ratio of the difference between the predetermined temperature and the solidus temperature over the predetermined period of time and which is higher than 10 000 C./sec.

28. The method according to claim 27, wherein the predetermined temperature is at least 75% of the liquidus/solidus temperature difference higher than the solidus temperature, the predetermined temperature being preferably equal to or higher than the liquidus temperature, and being more preferably at least 10 C. higher than the liquidus temperature.

29. The method according to claim 27, wherein the molten aluminium alloy composition is supplied through a piping to the at least one nozzle and is additionally heated in the piping before being ejected out of the nozzle, the piping being preferably substantially completely filled with the aluminium alloy composition.

30. The method according to claim 25, wherein the pieces of rapidly solidified material are plastically consolidated by plastic deformation under pressure at a temperature of at least 300 C., preferably of at least 400 C. and more preferably of at least 450 C.

31. The method according to claim 25, wherein the pieces of the rapidly solidified material are plastically consolidated at a temperature which is lower than the solidus temperature of the alloy, preferably at least 10 C. lower than the solidus temperature, but higher than 350 C., preferably higher than 375 C. and more preferably higher than 400 C., the temperature being most preferably comprised between 400 C. and 550 C.

32. The method according to claim 25, wherein the pieces of rapidly solidified material are consolidated by plastic deformation to reduce an average grain size of the consolidated aluminium alloy, measured in accordance with standard ASTM E2627-13 (2019) to a value of less than 2000 nm, preferably less than 1000 nm, more preferably less than 800 nm and most preferably less than 600 nm.

33. The method according to claim 25, wherein the pieces of the rapidly solidified material are consolidated by extruding them with a cross section reduction of at least 3, preferably of at least 6, more preferably of at least 8 and most preferably of at least 10.

34. The method according to claim 25, wherein the consolidated aluminium alloy is hot forged, in particular die forged.

35. The method according to claim 34, wherein the consolidated aluminium alloy is hot forged at a temperature higher than 400 C., preferably higher than 450 C. and more preferably higher than 475 C. or higher than 500 C., but lower than the solidus temperature of the alloy, preferably at least 10 C. lower than the solidus temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0117] Other advantages and particularities of the present disclosure will become apparent from the following description of some particular embodiments of the aluminium alloy and the method for producing it according to the disclosure. This description is only given by way of example and is not intended to limit the scope of the disclosure. The reference numerals used in the description relate to the annexed drawings wherein:

[0118] FIG. 1 shows schematically a possible embodiment of an installation for producing the molten aluminium alloy and for rapidly solidifying this alloy by a melt spinning device;

[0119] FIG. 2 is an SEM image showing the microstructure of the Al-7Mg-1V alloy with coarse primary Al.sub.3 V intermetallic phases produced in the RS example wherein the alloy composition was rapidly solidified at a temperature of 650 C.;

[0120] FIGS. 3 and 4 are similar to FIG. 2 but show the microstructure of the Al-7Mg-1V alloy rapidly solidified at a temperature of 750 C. and 850 C. and showing less or no coarse primary Al.sub.3 V intermetallic phases;

[0121] FIGS. 5 to 7 are TEM images, with an increasing magnification, of the Al-7Mg-2Mn-1V-1Cr alloy plastically consolidated at a temperature of 400 C.; and

[0122] FIG. 8 is a grain orientation map obtained from a TKD analysis of the Al-7Mg-2Mn-1V-1Cr alloy plastically consolidated at a temperature of 400 C.

DETAILED DESCRIPTION

[0123] The disclosure generally relates to a new aluminium alloy, in particular a wrought aluminium alloy, which is rapidly solidified and plastically consolidated. The aluminium alloy has a liquidus and a solidus temperature. The liquidus temperature is the lowest temperature at which the alloy, in an equilibrium state, is completely liquid while the solidus temperature is the highest temperature at which the alloy, in an equilibrium state, is completely solid. Both temperatures can be seen on the equilibrium phase diagram of the alloy. The microstructure and the composition of the alloy according to the disclosure enables to achieve a high yield strength at room temperature combined with a low hot deformation stress so that is can be easily formed by a hot forging, in particular by a hot die forging process. A high ductility can also be achieved in combination with a yield strength that is still high, in particular higher than 300 MPa. The rapidly solidified and plastically consolidated alloy has a quite high thermal stability so that its yield strength is not lost, or only to a limited extend, during a hot forging process. The liquidus temperature of the new aluminium alloy can be kept low in order to make alloying and solidifying the alloy easier, especially on an industrial scale.

[0124] The alloy may be a monolithic material and can be used as such to produce aluminium parts. However, it is also possible to include the alloy in a metal matrix composite (MMC) or in a metal matrix nanocomposite (MMNC) material. A metal matrix composite is a composite material with at least two constituent parts, one being the aluminium alloy. The other material may be a different metal or may be another material, such as a ceramic or an organic compound. MMCs are made by dispersing reinforcing material into a metal matrix. For example carbon fibres are commonly used in aluminium matrix. The matrix, i.e. the aluminium alloy, is the monolithic material into which the reinforcement is embedded and is completely continuous. MMNCs can be defined as a metal matrix composite that is reinforced by nano-reinforcements. The reinforcements in MMCs or MMNCs do not form part of the aluminium alloy that forms the matrix. The composition of the aluminium alloy according to the present disclosure is therefore given in percent by weight of the composing alloy elements not including any reinforcements when the aluminium alloy would be part of an MMC or an MMNC. Also the phase diagram defining the liquidus and solidus temperature of the alloy is only based on the aluminium alloy forming the monolithic matrix material.

[0125] The alloy according to the present disclosure comprises aluminium and different alloying elements, including alloying elements that provide for a solid solution strengthening effect and alloying elements that are intended to produce small, nanoscale dispersoids that assist in obtaining a fine grained alloy structure and that stabilize this fine grained structure. The refined grain structure provides for an additional strengthening effect enabling to achieve, in combination with the solid solution strengthening effect, a high strength. In this way, no cold working of the alloy is necessary to increase the strength thereof nor any separate/dedicated precipitation hardening of the aluminium matrix within the grains by additional strengthening heat treatment operations. Cold working and separate precipitation hardening operations are preferably avoided or kept to a minimum since both of these strengthening mechanisms have a negative effect on the plasticity/ductility of the alloy and delivers additional effort (cost) to production routines.

[0126] In general, the aluminium alloy according to the present disclosure comprises between 3.00 and 10.00 wt. % of Mg and between 1.00 and 6.00 wt. % of Mn. For higher strengths, it preferably comprises at least 4.00 wt. % of Mg. For lower strengths, but higher ductilities, if may comprise less Mg, in particular 3.00 wt. % or more or 3.5 wt. % or more Mg. The alloy moreover comprises one or more transition elements that are selected from the group consisting of Cr in a maximum amount of 1.50 wt. %, V in a maximum amount of 1.50 wt. %, Ti in a maximum amount of 1.00 wt. %, zirconium Zr in a maximum amount of 1.00 wt. %, Mo in a maximum amount of 1.50 wt. %, Co in a maximum of 1.50 wt. %, and Nb in a maximum amount of 1.00 wt. %. The total amount of these transition elements is at least 0.50 wt. %. Other elements may be present in the alloy but the alloy should contain no or less than 2.00 wt. %, preferably less than 1.00 wt. % of Zn, no or less than 2.00 wt. %, preferably less than 1.00 wt. % of Si, no or less than 1.00 wt. % of Sc and no or less than 1.00 wt. % of W. Finally, the alloy should contain no other elements different from Al, Mg, Mn, Cr, V, Ti, Zr, Mo, Co, Nb, Zn, Si, Sc and W or in total less than 4.00 wt. % of such other elements.

[0127] The aluminium alloy of the present disclosure is produced by preparing a molten aluminium alloy composition, by rapidly solidifying the molten aluminium alloy composition in the form of pieces of rapidly solidified material, and by plastically consolidating the pieces of rapidly solidified material. The plastically consolidated alloy is then preferably hot forged and optionally further machined to produce the desired parts.

[0128] Rapid solidification of the molten alloy composition is a mandatory step in the production of the alloy according to the present disclosure. The key element is to prevent the growth of inter-metallic phases during crystallisation of the molten alloy composition as well as segregation of the alloying elements to dendrite regions. In the alloy according to the present disclosure these phenomena are avoided by increasing the crystallisation rate by a fast cooling process. The cooling rate that can be achieved is limited physically by heat transfer phenomena and the heat capacity of the material. The dimensions of the material that is subjected to the cooling process has to be limited. In fact, in order to reach the required chemical composition very high cooling speeds are required that can be obtained by producing highly fragmented pieces of molten material. Two technologies can be used: powder atomisation and melt spinning. Both are characterised by a high surface to volume ratio enabling a fast heat extraction. Especially, a melt spinning process enables a more efficient heat extraction by making use of the efficient heat transfer between the molten alloy composition and a cold drum surface, preferably a copper drum surface. As a result of the rapid solidification technique, a solidified/crystallised material is produced in the form of a highly fragmented material, consisting of pieces having at least one dimension that is smaller than 100 m. Preferably, the pieces of solidified material have at least one dimension that is even smaller, in particular smaller than 80 m or even smaller than 60 m.

[0129] By the expression rapidly solidified is meant that when being solidified the molten aluminium alloy is cooled down at an average cooling rate that is higher than 10 000 C./sec (104 C./sec) and preferably higher than 100 000 C./sec (105 C./sec). The average cooling rate is in particular calculated over a time interval starting from the moment the accelerated extraction of heat from the liquid alloy composition has started until the average temperature of the alloy composition has dropped to its solidus temperature. The accelerated extraction of heat is preferably started as from an average temperature of the alloy composition that is equal to or higher than the liquidus temperature of the alloy composition. The average cooling rate is preferably higher than 10 000 C./sec (104 C./sec) and more preferably higher than 100 000 C./sec (105 C./sec) over the time interval between the moment in time when the alloy composition is at its liquidus temperature and the moment in time when the temperature of the alloy composition has dropped to its solidus temperature.

[0130] In practice, the molten aluminium alloy is rapidly solidified as from the moment it is ejected from one or more nozzles. As explained hereabove, the molten aluminium alloy ejected from the nozzle can be solidified, in a melt spinning process, in the form of ribbons or, in a powder atomisation process, in the form of a powder.

[0131] Rapid solidification starts when the molten aluminium alloy exits the nozzle or nozzles. At the outlet of the nozzle, the molten aluminium alloy has a predetermined temperature that is substantially uniform. If not uniform, this predetermined temperature is the volume weighted average temperature of the molten aluminium alloy upon exiting the nozzle. The average cooling rate has to be calculated over the interval wherein the volume-weighted average temperature of the molten aluminium alloy drops from the predetermined temperature at the outlet of the nozzle to the solidus temperature of the aluminium alloy. The difference between these two temperatures divided by the time it takes to cool the molten aluminium alloy down from the predetermined temperature to the solidus temperature is the average cooling rate that has to be higher than 10 000 C./sec (104 C. per second) to have a rapid solidification process.

[0132] When appropriate measurement devices are available, this average cooling rate can be measured but it can also be calculated based on different parameters. The required cooling rate can also be determined experimentally by testing incrementally increasing cooling rates starting from a cooling rate at which primary intermetallic phases are formed until a cooling rate is reached at which primary intermetallic phases are no longer formed during the rapid solidification step.

[0133] For a rapid solidification process by melt spinning the average cooling rate can be calculated based on calculations as disclosed in the article Analyses of the melt cooling rate in the melt-spinning process of B. Karpe et al. in Journal of Achievements in Materials and Manufacturing Engineering, Vol. 51, Issue 2, April 2012. The content of this article is incorporated herein by way of reference. In a number of the figures of this articles, the initial quick drop of the temperature from about 700 C. to 660 C., i.e. to the solidus temperature of pure aluminium, can be seen and this for different ribbon thicknesses and different distances from the surface of the chill wheel. When dividing this temperature drop by the solidification time, and averaging these values for the different distances from the surface of the chill wheel, the average cooling rate can be calculated.

[0134] For a rapid solidification process by gas (or liquid) atomisation the average cooling rate can be calculated based on calculations as disclosed in the article Rapidly Solidified Gas-Atomized Aluminium Alloys Compared with Conventionally Cast Counterparts: Implications for Cold Spray Materials Consolidation by Bryer C. Sousa et al., Coatings 2020, 10, 1035. The content of this article is incorporated herein by way of reference. The formula enabling to calculate the cooling rate is given in this article. In FIG. 3 of this article it can be seen that the cooling rate is in particular dependent from the particle size of the atomised droplets. Other parameters are the specific heat of the metal droplet and the thermal conductivity of the gaseous species utilized during gas atomisation.

[0135] FIG. 1 shows schematically an installation that can be used to produce the rapidly solidified aluminium alloy by a melt spinning process. This installation comprises a furnace 1 that is provided with a heater 2. As illustrated in FIG. 1 this heater 2 may be an induction heater 2. Other heaters are however also possible, for example gas heaters. The different elements of the aluminium alloy composition are introduced in this furnace, either as pure elements or as mixtures (master alloys) to produce the aluminium alloy composition 3 in the furnace 1. The aluminium may be added as substantially pure aluminium whilst the other alloying elements are preferably added in the form of a master alloy (that also contains a portion of the aluminium).

[0136] The furnace 1 is connected by a piping 4 to a nozzle 5 and can be closed by means of a valve that is not shown in FIG. 1. The piping 4 comprises one pipe 6. This pipe 6 is provided with a further heater 7, which is again an induction heater 7 provided around the pipe 6. The pipe 6 has a widened section forming a chamber 11 that is also heated by a heater 7. The aluminium alloy composition 3 is heated to a first temperature in the furnace 1 and is fed at this temperature to the inlet of the piping 4. The furnace 1 and the piping 4 are arranged vertically one above the other so that the molten alloy composition 3 can flow by gravity from the furnace 1 to the nozzle 5. An extra pressure can be applied onto the molten composition 3 by closing the furnace 1 by means of a lid 8 and by introducing gas under pressure into the furnace 1. Alternatively, a pump (not shown) may be provided in the piping 4. The piping 4, and also the chamber 11 formed by the piping 4, is preferably completely filled with the molten alloy composition so that the molten composition flows by pipe-flow through the piping. In this way, no or substantially no gas, for example air containing water vapour, is present in the piping so that the alloy composition is not subjected to any oxidation processes within the piping 4.

[0137] The molten aluminium alloy that is ejected from the nozzle 5 arrives on a rotatable chill roll 9 that may be made for example of copper, copper-beryllium or stainless steel. The roll 9 is cooled internally, for example by means of water, and is rapidly rotated to achieve the required fast cooling rates. The liquid aluminium alloy is solidified in the form of a ribbon 10, or in the form of several ribbons in case more nozzles 5 are provided at the end of the piping 4 (that may contain more than one or several pipes 6 in parallel). The ribbon thickness can be controlled by the rotational speed of the chill roll 9, the ejection pressure, the nozzle slot size and the gap between the nozzle 5 and the roll 9. Higher cooling rates can be achieved by reducing the ribbon thickness, in particular to the above-described preferred maximum dimensions of 1.00, 0.80 or 0.60 m. The ribbon may have a width of one to several millimetres, for example a width of between 1 to 10 mm, in particular between 1 and 5 mm.

[0138] Instead of using a chill roll 9 for rapidly solidifying the molten alloy, it can also be solidified rapidly by other existing methods, in particular by a spray forming process wherein the molten alloy is atomized in the form of droplets out of the nozzle to produce a powder. The droplets are either cooled in the air or with a liquid such as water (in particular in accordance with a granulation technique) in order to further increase the cooling rate. The nozzle may also eject the molten alloy in water, in particular in accordance with the known in-rotating water quenching technique.

[0139] Instead of producing the molten alloy composition in one furnace 1, it is possible to inject one or more of the other alloying elements in the piping 4, or in a mixing chamber provided in the piping 4, which is part of the piping 4 and which is thus also preferably completely filled with the molten alloy composition.

[0140] An important advantage of the additional heating step by means of the further heater 7 is that the aluminium alloy composition contained in the furnace 1 does not need to be molten completely, and has in particular not to be heated to its liquidus temperature. When some of the alloying elements are injected in the piping 4, the liquidus temperature of the fraction of the alloy composition contained in the furnace 1 may moreover be reduced, optionally to such an extent that this fraction of the alloy composition may be heated to its (lower) liquidus temperature whilst still avoiding or minimizing oxidation of the aluminium in the furnace. In this way no vacuum or no inert gas has to be applied in the furnace 1. By the additional heating step in the piping 4, and especially in the chamber 11 comprised therein, the entire alloy composition is then heated to a higher temperature at which the entire alloy composition is completely, or substantially completely, molten before being ejected out of the nozzle 5. The chamber 11 is intended to increase the residence time of the alloy in the piping 4. The increased residence time enables any alloying element that has not yet been completely molten/dissolved in the molten alloy to further dissolve therein. Preferably, the molten aluminium alloy is heated in the piping to a temperature that is equal to or higher than its liquidus temperature, preferably to a temperature that is at least 10 C. or even 20 C. higher than its liquidus temperature.

[0141] The molten aluminium alloy composition that is ejected from the nozzle 5 has a predetermined temperature upon exiting the nozzle and is rapidly solidified by being cooled down within a predetermined period of time to the solidus temperature of the aluminium alloy. For a rapid solidification process, the average cooling rate, which is determined as the ratio of the difference between the predetermined temperature and the solidus temperature over the predetermined period of time, should be higher than 10 000 C./sec (104 C./sec) and preferably even higher than 100 000 C./sec (105 C./sec). A rapidly solidified aluminium alloy is an alloy that is rapidly solidified as from a temperature that is at least 75% of the difference between the liquidus and the solidus temperature of the aluminium alloy higher than its solidus temperature. When being ejected from a nozzle, the molten aluminium alloy exiting the nozzle should thus have such a high predetermined temperature. This predetermined temperature is preferably equal to or higher than the liquidus temperature of the alloy, and more preferably at least 10 C. higher than this liquidus temperature. When rapidly solidifying the aluminium alloy from such a high temperature, the formation of primary intermetallic phases can be avoided so that the alloy is substantially free of primary intermetallic phases and preferably also of dendrites.

[0142] Since the rapidly solidified material is produced in the form of pieces, in particular of ribbons 10, of rapidly solidified material, those pieces of rapidly solidified material have to be plastically consolidated in a next step to produce solid pieces of the alloy that can be further processed, by hot forging and/or machining, into the final articles. When produced in the form of ribbons, the pieces of rapidly solidified material could be first chopped into smaller pieces. In this way, the particles/pieces of rapidly solidified material can more easily be compacted to remove the gaps/voids between these particles.

[0143] Plastic consolidation is a required step to convert the fragmented rapidly solidified material into the useful consolidated bulk form, i.e. into solid pieces of the alloy material. To achieve this, the separate pieces (particles) of solidified material have to be put together in a very close contact enabling the formation of new interatomic bonds. A very close contact is however not sufficient as such since aluminium and its alloys form continuous and tight layers of oxides on their surfaces (that is often called aluminium passivation). In other words because of these oxidation processes there is no fresh metal surface available for correct bonding. A second requirement that thus has to be fulfilled during plastic consolidation is the creation of oxide free surface portions on the particles. During the plastic consolidation step, the separate particles are preferably compressed together in an enclosed space and subjected to forces forcing them to change their initial shape. By doing so, the two above mentioned requirements are met simultaneously. From a physical point of view the plastic consolidation process is characterised by a stress component having a large hydrostatic component to press the particles closely together and a shear component deforming the particles. When pressing the particles together, they are somewhat deformed to remove the gaps between the particles. As a result of the shear stresses, however, the surface to volume ratio of the particles is always increasing thus creating/exposing new oxide free surface portions.

[0144] The easiest way to obtain the combination of the required pressure and shear stresses on an industrial scale is by an extrusion process. Preferably, the pieces of rapidly solidified material are first compacted to form a billet that is preheated and then extruded through a die opening. An important parameter of the extrusion process is the cross section reduction ratio 2, which is the ratio between the cross sectional area of the billet to the cross sectional area of the extruded part leaving the die opening. The cross section reduction area is preferably at least equal to 10. Smaller cross section reduction areas are however also possible, especially in case the extruded aluminium alloy is subsequently hot forged, in particular die forged. During such hot deformation steps, the produced part is indeed further plastically consolidated. The extrusion process can moreover be followed by one or more further plastic consolidation processes.

[0145] Instead of an extrusion process, or in addition thereto, other consolidation techniques can be applied, for example multistep forging, ECAP (Equal Channel Angular Pressing) or any other techniques characterised by the above described tensor can be used for plastic consolidation purposes. In particular ECAP can be used after the extrusion process, especially when the extrusion process was done with a small cross section reduction ratio. The ECAP process can be carried out directly onto the extruded parts so that they are still hot. During the ECAP process material is pressed through a die consisting of two intersecting channels with identical cross sections. An advantage of the ECAP process is that the cross section of the part is thus not changed, in particular not reduced. In the ECAP process, the part is subjected to severe plastic deformation that contributes not only for grain refinement but also for additional fracture and refinement of the oxide layers between the aluminium pieces/particles. More than one ECAP step can be carried out successively.

[0146] Before subjecting the rapidly solidified material to the plastic consolidation step it is heated to a predetermined temperature, i.e. to the temperature at which the plastic consolidation process is carried out. The indicated temperatures are the volume-weighted average temperatures of the rapidly solidified materiel, in particular of the billet of the rapidly solidified materiel that is being plastically consolidated, in particular extruded. Higher plastic consolidation temperatures are promoting consolation effectiveness. Alloy flow stress is lower at higher temperatures, facilitating the deformation of the initial particles (pieces of the rapidly solidified material) to achieve close contact and produce new oxide free surface portions. Additionally higher temperatures are increasing local diffusion processes improving the effectiveness of the inter-particles bonding. The ultimate upper limit for the consolation temperature is connected to the solidus temperature of the alloy. For the alloys according to the present disclosure, the magnesium content is controlling the lowest melting point (solidus temperature) of the alloy, i.e. the temperature at which the alloy starts to melt when being heated up. During all processing steps after the rapid solidification, the material has to be in the solid state. Any local melting will cause close to equilibrium structure formation, characterised by chemical segregations and by the formation of larger inter-metallic phases. In case of the alloy according to the present disclosure, magnesium is controlling the lowest value of the melting temperature range. Particularly, depending on the magnesium concentration the melting point (solidus temperature) of the alloys is in the range of about 550 C. to about 590 C. for magnesium concentrations between 4 and 7 wt. % and is decreasing when the magnesium concentration increases. An additional constraint on the plastic consolidation temperature is imposed by the diffusion processes. A higher temperature means more intense diffusion and faster coarsening of the structure of the alloy. The preferred temperature processing window for the plastic consolidation is between 400 C. and 500 C. Within this preferred temperature range the flow stresses are small enough for effective plastic consolidation in a typical industrial press, and diffusion is not too severe to destroy the highly refined dispersoid based microstructure of the alloy.

[0147] As a result of the plastic consolidation a highly refined microstructure of the consolidated material is achieved. Different processes of structure refinement are acting at the same time. Deformations imposed by the external forces are creating large amounts of dislocations that are the driving forces for recrystallization processes. This is called dynamic recrystallization. The final state of the microstructure is dependent on the intensity of these processes: the imposed deformation tending to decrease the grain size whilst the higher temperature tending to increase it. The alloy composition according to the present disclosure enables however to shift the balance towards smaller grains by the thermal stabilization of the alloy structure. In the alloy according to the present disclosure small inter-metallic phases/dispersoids are indeed produced as grain boundary stabilising elements. The more of such nano-metric phases that are present in the microstructure, the better the pinning effect that can be achieved. Those phases/dispersoids are also formed in situ during the plastic consolidation process. The aluminium matrix is oversaturated in the alloying components, and where suitable conditions are given (high temperature and diffusion paths) dispersoids will form. The low diffusion coefficient of the alloying elements considerably limits the growth of the dispersoids. The final grain size thus depends upon the processing conditions as well as on the number and size of dispersoids. With the alloy composition according to the present disclosure, grain sizes in the range of 500 nm can easily be obtained. Such small grain sizes significantly boost the mechanical strength of the alloy in cold condition. Moreover, low flow stresses can be achieved at higher temperatures, i.e. during the hot forging steps.

[0148] The plastic consolidation process may result directly into the final component that is in particular in the form of an extruded profile. Usually, an additional hot forging/forming step will however be applied. During hot forming, the same temperature constrains apply as during the plastic consolidation process. The same mechanisms apply, where microstructure is dynamically rebuild during deformation processes (dynamic recrystallization). The alloy according to the present disclosure enables however to apply higher temperatures during the forming step in order to makes the forming step easier. Although some strength will be lost when applying higher forming temperatures, the initial strength of the plastically consolidated alloy can be sufficiently high to allow the use of such higher forming temperatures. By the resulting coarsening of the alloy structure, the thermal stability of the final part is moreover increased to some extent.

[0149] The finer grain structure of the plastically consolidated alloy allows to activate grain boundary sliding processes during the next hot deformation steps. Positive aspects include smaller forming presses, smaller and cheaper tooling and prolonged life of tooling. The finer grain structure also enables to obtain a ductile alloy that still has a high strength. The ductility of the alloy can in particular be increased by reducing the amount of Mg and by optionally increasing the amount of Mn. Additionally the higher thermal stability provided by the finely dispersed alloying elements allows processing in an isothermal forming regime. This means that during the plastic deformation, the temperature can be kept nearly constant. In this way the temperature can be better controlled and an improved material flow can be achieved thus enabling near net shape forming.

[0150] During the forming steps after the plastic consolidation the microstructure of the alloy will normally be coarsened to some extent. During hot deformation diffusion processes are intensified (there are more diffusion paths active, in particular dislocation cores and new grain boundaries) leading to dispersoid and grain coarsening. The final effect is dependent on the processing conditions. After the plastic consolidation, the alloy preferably has an average grain size of less than 2000 nm, preferably of less than 1000 nm, more preferably of less than 800 nm and most preferably of less than 600 nm. In combination with the small size of the dispersoids, such a fine grain structure enables to activate grain boundary sliding during hot deformation. After the hot forging step, the average grain size of the alloy is preferably still smaller than 4000 nm, preferably smaller than 2000 nm, more preferably smaller than 1500 nm and most preferably smaller than 1200 nm. After the hot forging step, the small grain size is especially important to improve the mechanical strength of the alloy.

[0151] The strength of the alloy according to the disclosure is directly connected to two strengthening mechanisms, namely to solid solution strengthening and grain size strengthening (following the Hall-Petch rule). When a grain size is produced that is in the order of magnitude of 500 nm, a yield strength higher than 600 MPa can easily be achieved with an alloy according to the present disclosure. Since the alloy is produced under hot conditions, the dislocation density is low and the plasticity of the alloy is not deteriorated. For lower yield strengths, higher ductilities can thus also be obtained. This is in contrast to cold forming/working steps during which the dislocation density increases leading to strengthening of the material but at the same time to a loss of plasticity. Also the dispersoids produced during the plastic consolidation process are preferentially produced at the grain boundaries to stabilize the fine grained structure and to enable grain boundary sliding. Precipitation hardening of the aluminium matrix as such is thus avoided or at least minimized. This is advantageous in that precipitation strengthening of the alloy has a negative effect on the flow stress of the alloy during hot deformation whilst grain size strengthening of the alloy reduces the hot flow stress of the alloy and may give the alloy even superplastic properties. Dedicated precipitation hardening steps can be applied but are preferably omitted. Lack of precipitation strengthening routine results in additional benefits as usually performed in standard alloys, requires additional heat treatment steps, increasing cost of the products by additional time, infrastructure and energy use. Moreover, alloys with a higher ductility can be obtained.

[0152] The following examples illustrate some embodiments of alloys of the present disclosure, a production method thereof and some of the advantageous properties that can be provided by the alloys according to the disclosure.

Example of Alloying and Rapid Solidification Technique

[0153] A ternary alloy composition was made consisting of aluminium, 7 wt. % of magnesium and 1 wt. % of vanadium. The alloy composition was made and rapidly solidified in an installation as shown schematically in FIG. 1.

[0154] Based on the binary Al-V phase diagram the alloy would have, in the absence of magnesium, a liquidus temperature of about 820 C. The aluminium, magnesium and the vanadium were applied in the furnace 1 and were heated therein to a temperature of 650 C. This temperature is lower than the solidus temperature of pure aluminium (660 C.) but the solidus temperature of the aluminium/magnesium solid solution is considerably lower (only about 550 C.). The alloy composition was only partially molten and contained, based on the phase diagram, an amount of undissolved Al.sub.3V intermetallic phases.

[0155] The partially molten alloy composition was further heated in the chamber 11 by means of the further heater 7 and was then rapidly solidified by melt spinning onto the water cooled copper chill roll 9. The produced ribbons 10 had a thickness of about 50 m and a width of about 3 mm. The residence time of the alloy in the chamber 11 was equal to about 30 s.

[0156] FIG. 2 shows the microstructure of the rapidly solidified alloy composition that has not been extra heated by means of the heater 7. A high number of primary Al.sub.3V intermetallic phases with a maximum diameter not higher than 20 m can be seen.

[0157] FIGS. 3 and 4 show the microstructures of the rapidly solidified alloy compositions that have been extra heated by means of the heater 7 to a temperature of 750 C. and 850 C. respectively. In the structure of FIG. 3 there are a lot less (only one) particles formed by Al.sub.3 V intermetallic phases whilst in FIG. 4 there are no longer intermetallic particles larger than 1 m. As a matter of fact, the alloy was heated to a temperature higher than its liquidus temperature so that the molten alloy did not contain any primary intermetallic phases. The alloy was moreover rapidly solidified so that no primary intermetallic phases could be formed during the crystallization phase, i.e. when cooling down from its liquidus temperature to its solidus temperature.

[0158] In this last experiment, the distance between the location where the liquid alloy composition was applied onto the roll 9 and the solidification front was determined with a camera. It took about 0.00025 s for the alloy to reach the solidification front. The temperature of the alloy composition dropped in this period of time on the roll 9 from about 850 C. to about 550 C., thus at an average cooling rate that could be estimated at about 1 200 000 C./s.

Examples of Alloy Compositions and Mechanical Properties

[0159] A number of different alloys according to the present disclosure and a number of comparative alloys have been prepared. The composition and the mechanical strength of the alloys are presented in the table 1.

[0160] Tables 1a and b: Composition (in wt. %) and mechanical strength (HV: hardness in Vickers Hardness, YS, R.sub.0.2: true yield strength in MPa) of rapidly solidified and plastically consolidated alloys, including alloys according to the present disclosure and comparative alloys.

TABLE-US-00001 TABLE 1a Alloy No. 1 2 3 7 8 9 (comp) (comp) (comp) 4 5 6 (comp) (comp) (comp) Al Bal Bal Bal Bal Bal Bal Bal Bal Bal Mg 5 5 5 5 5 6 7 7 7 Mn 2 2 2 Zn 2 V 1 1 1 1 1 Cr 1 1 1 1 1 Zr Ti Co Sum 0 1 1 2 4 2 0 1 1 HV 91 109 126 184 176 192 98 132 144 YS 205 264 310 586 573 604 211 410 415

TABLE-US-00002 TABLE 1b Alloy No. 10 11 12 13 14 15 16 17 18 19 20 21 Al Bal Bal Bal Bal Bal Bal Bal Bal Bal Bal Bal Bal Mg 7 7 7 7 7 7 7 7 7 7 7 7 Mn 2 2 2 2 2 2 2 2 3.5 2 2 2 Zn V 1 1 0.5 1 0.5 0.5 0.25 0.5 1 0.5 0.5 1 Cr 1 0.5 0.5 0.5 1 1 1 1 0.5 0.5 0.5 Zr 0.5 0.5 0.25 Ti 0.5 0.25 0.2 Co 0.25 0.25 Sum 1 2 1 1.5 1.5 2 1.75 1.75 2 1.45 1.25 1.75 HV 183 200 186 191 192 202 195 193 223 193 190 196 YS 552 624 584 581 629 650 636 625 719 594 600 646

[0161] Alloy numbers 20 and 21 could also be produced by replacing all of the Co or a portion thereof with similar amounts of Mo or Nb. This results in alloys with a similar hardness and yield strength as alloys numbers 20 and 21.

[0162] All compositions are given in weight percent with aluminium balanced to 100%. The row sum indicated the total amount of dispersoid forming elements, i.e. of all the elements different from Al, Mg and Mn. The alloys prepared with the indicated composition were heated to a temperature above their liquidus temperature and were rapidly solidified by casting on a copper drum and then extruded at a temperature of 400 C. with an area reduction ration of 16. The composition was varied to show the influence of the solid solution strengthening elements as well as of the dispersoid forming elements on the mechanical properties expressed in terms of material hardness (determined by compression) and yield strength (measured by an elongation test).

[0163] First of all, the yield strengths of the different alloys were found to show a linear correlation with the hardness values, more particularly according to the equation:

[00003]$\mathrm{YS}=4.0876\mathrm{HV}-175.65,$ [0164] with R.sup.2 being equal to 0.98.

[0165] The Vickers' hardness values are thus a good indication of the tensile strength of the alloys.

[0166] Table 1 shows that the highest strength is achieved by simultaneous addition of solid solution strengthening elements and of dispersoid forming elements. The data in the table allow to analyze the influence of the particular elements on the mechanical properties of the material.

[0167] For example, keeping the amounts of the other elements constant, an increasing Mg content of 5 wt. %, 6 wt. % and 7 wt. % (see alloys Nos. 4, 6, 11), is giving hardness values of 184HV, 192HV and 200HV respectively. Increase of the Mg content is thus giving clear advantages in terms of the material strength. It is also important to mention that an increase of the Mg content was also found to prevent grain growth during hot forming processes, leading to the formation of smaller grain sizes.

[0168] A similar effect can be observed for an increasing content of Mn. For example, adding 2 wt. % Mn to the alloy containing 7 wt. % Mg and 1 wt. % V improves the hardness from 132HV to 183HV (see alloys Nos. 8 and 10) whilst an increase of the Mn content from 2 to 3.5 wt. % increases the hardness from 200HV to 223HV (see alloy Nos. 11 and 18). Apart from its solid solution strengthening effect, Mn also creates small dispersoids leading to an additional increase of the strength.

[0169] Not all elements were found to have a positive effect on the solid solution strengthening. Comparing alloys 4 and 5, it can be seen that addition of a considerable amount of Zn had a negative effect on the final mechanical properties. Such effect can be attributed to the formation of various phases containing Mg and Zn that may provide in other alloys for a solution strengthening and precipitation hardening of the alloy but which in the alloys according to the present disclosure effectively depletes the solid solution from Mg content. Other elements that are typically added to aluminium alloys, such as for example copper, have not been tested since they have a negative impact on the corrosion resistance of the alloy.

[0170] A similar analysis can be performed for the dispersoid forming elements. It is clear that an increase of their concentration leads to a significant improvement of the hardness. Based on the data of the different alloys that contain 7 wt. % Mg and 2 wt. % Mn (alloy Nos. 10-17 and 19-21), the following linear relationship was found between the sum of the amounts of the different dispersoid forming elements (V, Cr, Zr, Ti and Co) and the hardness of the alloy:

[00004]$\mathrm{HV}=13.965\mathrm{sum}+171.53,$

with R.sup.2 being equal to 0.89.

[0171] Based on this relationship, a minimum amount of 0.5 wt. % of dispersoid forming transition elements would enable to achieve a hardness of about 180HV, or a corresponding yield strength of about 560 MPa.

[0172] The effect on the hardness value (and thus also on the tensile strength of the alloy) does not only depend on the amount of dispersoid forming elements but also on the element itself and on the specific combinations thereof (this is why the R.sup.2 value for the linear equation is somewhat smaller). For example from alloy Nos. 2 and 3 and also from alloy Nos. 8 and 9 it appears that Cr has a somewhat higher strengthening effect than V.

[0173] It is important to stress out that the dispersoid forming elements do not only have an effect on the strength of the alloy but that they also provide for the required grain stabilizing effect. It is also an important finding, that several dispersoid forming elements can be used simultaneously, each in a smaller content, making it thus possible to decrease the required casting temperature of the alloy (i.e. the liquidus temperature). The highest strengthening effects are obtained with compositions wherein the sum of the dispersoid forming elements is at least equal to 2 wt. %. According to the binary AlCr and AlV phase diagrams, 2 wt. % of Cr would result in an alloy having a liquidus temperature of 780 C. whilst 1.7 wt. % of V would result in an alloy having a liquidus temperature of about 950 C. By using 2% of a combination of Cr and V, the liquidus temperature, and thus the required casting temperature, can be reduced.

[0174] The liquidus temperature can further be reduced by using three or more dispersoid forming elements, such as for example in alloy nos. 14-17 and 19-20. The liquidus temperature can especially be lowered by reducing the amount of vanadium. Using more different dispersoid forming elements appear to produce some synergetic effects on the yield strength. This can be seen when comparing alloy no. 11 with alloy no. 10 and alloy no. 14 with alloy no. 13.

Microstructure of Alloy No. 11: Al-7Mg-2Mn-1V-1Cr

[0175] The microstructure of this alloy is shown in FIGS. 5 to 8. The alloy was rapidly solidified and plastically consolidated by extrusion at a temperature of 400 C. Transmission electron microscopy (TEM) micrographs are showing a high number of dispersoids and a grain size below 1 m. The dispersoids are mainly located in the grain boundary regions, nonetheless in locations where the supersaturation of the alloy with chemical components was higher dispersoids can also be seen inside the grain regions (FIG. 6). A higher magnification of the alloy microstructure shows that the size of the dispersoid is in the range below 50 nm (FIG. 7). Both the high number and the small size of the dispersoids promotes stabilization of the grains during forming processes. Due to the low diffraction contrast between adjoining grains in the TEM micrographs, the small grain size cannot be seen clearly. Transmission Kikuchi diffraction (TKD) methodology was used in order to extract more detailed information about the grain size.

[0176] The TKD technique is characterized by a high spatial resolution that is required for sub-micron materials and to provide correct statistical information about microstructure features. A typical microstructure of the Al-7Mg-2Mn-1V-1C alloy acquired using TKD is shown in FIG. 8. The average grain size calculated in accordance with standard ASTM E2627-13 (2019) is 510 nm.

Examples Demonstrating Low Forming Stresses

[0177] The high strength of the alloys according to the disclosure at room temperature is coupled with a low flow stress in hot forming conditions. Exemplary results for the RS alloys are provided in Table 2 and compared to the one from the most common, medium strength, EN-AW 6082T6 alloy, which has been precipitation hardened by a T6-temperature treatment, and the technical purity aluminium EN-AW1050. Data were obtained from compression tests performed with a deformation speed of 10.sup.2 s.sup.1. The flow stresses are the maximum flow stresses when compacting a sample of the alloy at the indicated temperature to 50% of its initial height.

TABLE-US-00003 TABLE 2 True yield strength (YS, R.sub.0.2 in MPa) at room temperature and flow stress (FS in MPa) at elevated temperatures of various alloys deformed at high temperatures Al-7 Mg-2 Al-7 Mg-2 Al-7 Mg-2 Mn- Mn- Mn- EN-AW EN-AW 1 V-1 Cr 1 V-0.5 Cr 0.5 V-0.5 Cr 6082 1050 YS 624 581 584 370 (T6) 60 20 C. FS 10 8 7 500 C. FS 7 5 4 18 10 525 C. FS 3.5 2 1.5 17 7 550 C.

[0178] The alloys with the high strength at room temperature shows very low flow stresses in hot forming conditions. Depending on the deformation temperature, the flow stresses are in the range of 10 to 1.5 MPa. At 525 C., the flow stress is only about 1% or even less of the yield strength of the alloy at 20 C. whereas the flow stress of the most common EN-AW 6082T6 alloy is about 5% of its yield strength at room temperature. Moreover, the yield strength of this alloy was determined after being precipitation hardened whilst the flow stress was measured before being precipitation hardened, i.e. when the alloy had a much lower yield strength (in the order of magnitude of 110 MPa). The flow stress was thus equal to about 15% of its yield strength without the T6 thermal treatment.

[0179] It is well known that solid solution strengthening is also present in high temperature forming conditions. The opposite effect for RS alloys that have a high concentration of dispersoid forming elements is a result of the grain boundary sliding phenomena, being active for sub-micron sized materials. In the article of T. Tokarski et al. (2012) described hereabove, a decrease of the flow strength was also achieved by the fine grain size of the alloy. The flow stress at 450 C. could be reduced from 48 MPa to 19 MPa, but the alloy had a lower strength, namely a yield strength at room temperature of only 320 MPa. The high strength aluminium alloy Al-7Mg-2Mn-1V-1Cr had, on the contrary, only a flow stress of about 16 MPa at 450 C., combined with a high yield strength of 624 MPa. Moreover, the high strength aluminium alloy according to the present disclosure has a higher thermal stability, and may moreover loose only a small part of its strength, so that it can be hot deformed at higher temperatures, thus enabling much lower hot forming stresses.

Examples of Ductile High Strength Alloys

[0180] The alloys according to the disclosure may not only have a high strength at room temperature but may also have a high elongation combined with a strength that is still high. Table 3 shows the composition and mechanical properties of six rapidly solidified and plastically consolidated alloys according to the present disclosure, including two alloys (alloys nos. 22 and 23) that have an elongation higher than 15% and four alloys (alloys nos. 24 to 27) that have a smaller elongation but a higher yield strength.

TABLE-US-00004 TABLE 3 Composition (in wt. %), mechanical strength (YS, R.sub.0.2: true yield strength in MPa and UTS: ultimate tensile strength in MPa) and percent elongation at fracture (El. in %) of rapidly solidified and plastically consolidated alloys and of two solutionised and artificially aged (T6 treated) standard alloy compositions. Alloy No. EN-AW EN-AW 22 23 24 25 26 27 6082 (T6) 6061 (T6) Al Bal Bal Bal Bal Bal Bal Bal Bal Mg 3.5 4.5 6 7 5 7 Mn 2.5 2.5 2.5 2.5 4 3 Fe 0.25 0.5 V 0.5 0.5 0.5 0.5 0.5 0.5 Cr 0.1 Zr 0.25 0.25 0.25 0.25 0.25 0.25 Sum 0.85 0.75 0.75 0.75 0.75 0.75 YS, R.sub.0.2 350 375 460 490 510 530 370 330 UTS 470 480 555 560 570 585 400 350 El. 19 18 9 4 4 3 8 7.5

[0181] Alloys nos. 22 to 27 all have a yield strength that meets equation (1) and even equation (2), i.e. a yield strength in MPa that is higher than 525 or 530 minus ten times the percent elongation at fracture.

[0182] The heat treated standard alloys EN-AW 6082 and EN-AW 6061 have a similar yield strength as alloys nos. 22 and 23 but have a much lower elongation.

[0183] The alloys according to the present disclosure therefore do not only provide high to very high yield strengths but can even provide a combination of a high elongation with a high yield strength thus providing new opportunities in applications, such as automotive applications, wherein a low weight has to be combined with a high strength and a high ductility.

Examples Demonstrating Improved Thermal Stability

[0184] One of the unique feature of the alloys according to the present disclosure is the possibility to withstand higher forming temperature without significant loss of its mechanical properties. It allows to produce ready to use components in a hardened state. Examples of alloy hardness after hot forming processes is presented in Table 3. A hot forming process was simulated by means of a compression test, wherein the alloys plastically consolidated (extruded) at 400 C. where deformed to 50% of their initial height. The thermal stability tests was carried out in a temperature range of 450 C. to 550 C. at a deformation speed of 10.sup.2s.sup.1. An increase of the forming temperature to 50 C. above the extrusion temperature lead to approximately 5% loss of the initial hardness. As the temperature is increased, loss of hardness is higher; however, it does not exceed approx. 20% in the most extreme case of 550 C. (550 C. is the temperature just below the solidus temperature of the tested alloys). Depending on the desired final strength of the hot formed component a suitable temperature can be chosen, taking into account that an increased temperature will result in lower forces during the shaping process.

TABLE-US-00005 TABLE 3 Vickers hardness of the alloys after the hot forming processes at different temperatures. Al-7 Mg-2 Al-7 Mg-2 Mn-1 V-0.5 Cr Mn-0.5 V-0.5 Cr As extruded at 190 186 400 C. Compr. 181 178 450 C. Compr. 170 164 500 C. Compr. 168 156 525 C. Compr. 150 143 550 C.