Aluminum Alloy, in Particular for a Casting Method, and Method for Producing a Component from Such an Aluminum Alloy

Abstract

An aluminum alloy, in particular for a casting method, where the aluminum alloy includes at least aluminum, magnesium, manganese and copper. The aluminum alloy includes 0.001 to 0.50 wt. % of molybdenum, 0.05 to 0.4.5 wt. % of magnesium, 0.05 to 0.60 wt. % of manganese, up to 1.5 wt. % of iron, 0.25 to 4.00 wt. % of copper and 0.001 to 0.25 wt. % of vanadium.

Claims

1.-7. (canceled)

8. All aluminum alloy, comprising: aluminum; 0.001 wt. % to 0.50 wt. % molybdenum; 0.05 wt. % to 0.45 wt. % magnesium; 0.05 wt. % to 0.60 wt. % manganese; up to 1.5 wt. % iron; 0.25 wt. % to 4.00 wt. % copper; and 0.001 wt. % to 0.25 wt. % vanadium.

9. The aluminum alloy according to claim 8, wherein the manganese is at least 0.10 wt. % and less than 0.40 wt. %.

10. The aluminum alloy according to claim 8 further comprising 8.0 wt. % to 11.0 wt. % silicon.

11. The aluminum alloy according to claim 8 further comprising: at most 0.3 wt. % titanium; at most 0.3 wt.% zirconium; at most 400 parts per million strontium; at most 1.5 wt. % zinc; at most 0.25 wt. % chromium; at most 0.20 wt. % nickel; and at most 0.15 wt. % cobalt.

12. A method, comprising the steps of: producing a component from an aluminum alloy according to claim 8 by casting, without pressure or pressurized at an effective pressure of between 0 bar and 1,000 bar.

13. The method according to claim 12, wherein the aluminum alloy is cast into a mold at a temperature of 650 C. to 730 C.

14. The method according to claim 12, wherein the aluminum alloy is cast at a temperature of 580 C. to 650 C. thixotropically, without pressure or pressurized at an effective pressure of between 0 bar and 1,000 bar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 schematically shows a backscatter electron image (BSE image) of the alloy 233 comprising copper (Cu) and molybdenum (Mo) in the heat treatment state T5mod, in which, for example, a component designed as a crankcase and made of the specified alloy is produced by means of diecasting;

[0014] FIG. 2 schematically shows a BSE image of the alloy 226D (AlSi10Cu3) in the heat treatment state T5mod, in which a crankcase for example is produced from the alloy;

[0015] FIG. 3 is a BSE image of the alloy 233 comprising Cu and Mo in the heat treatment state T6red;

[0016] FIG. 4 is a BSE image of the alloy 226D in the heat treatment state T6red;

[0017] FIG. 5 is a diagram for illustrating mechanical characteristics of the component formed from the respective alloys at room temperature; and

[0018] FIG. 6 is a diagram for illustrating mechanical characteristics of the component produced from the respective alloys at 150 C.

DETAILED DESCRIPTION OF THE DRAWINGS

[0019] In the drawings, elements that are the same or functionally the same are provided with the same reference signs.

[0020] FIGS. 1 to 4 each show backscatter electron images (BSE images) of alloys from which the respective components are produced. The alloy is in each case, for example, an aluminum alloy, in particular an aluminum casting alloy and in this case preferably a heat-resistant aluminum casting alloy.

[0021] The component produced by the respective alloys is in each case, for example, a component used in a drivetrain of a motor vehicle, the component being, for example, a crankcase, in particular a diecast crankcase. This means that the component made of the respective alloys is produced by means of casting, in particular diecasting. In particular, the component can be a thick-walled component which has a wall thickness in a range of from 4 millimeters to 30 millimeters inclusive. By means of the aluminum alloy described in more detail in the following, particularly advantageous properties, in particular mechanical properties, of the component can be realized. Preferably, the aluminum alloy in each case has the following composition:

[0022] 8.0 wt. % to 11.0 wt. % silicon,

[0023] 0.25 wt. % to 4.00 wt. % copper,

[0024] 0.10 wt. % to 0.50 wt. % magnesium,

[0025] 0.05 wt. % to 0.60 wt. % manganese,

[0026] less than or equal to 0.3 wt. % titanium,

[0027] less than or equal to 0.3 wt. % zirconium,

[0028] less than or equal to 400 parts per million (ppm) strontium,

[0029] at most 1.5 wt. % iron,

[0030] at most 1.5 wt. % zinc,

[0031] 0.001 wt. % to 0.25 wt. % vanadium,

[0032] additional additives of 0.01 wt. % to 0.50 wt. % molybdenum,

[0033] at most 0.25 wt. % chromium,

[0034] at most 0.20 wt. % nickel,

[0035] at most 0.15 wt. % cobalt,

[0036] and the remainder aluminum, it being possible for impurities or additional elements to be optionally provided in a proportion of less than 0.05 wt. %.

[0037] Particularly preferably, the aluminum alloy comprises magnesium at at least 0.10 wt. % and less than 0.30 wt. %. Alternatively or additionally, the aluminum alloy preferably comprises manganese at at least 0.10 wt. % and less than 0.40 wt. %. By reducing the manganese concentration, the extensive primary formation of iron-manganese-containing intermetallic Al.sub.15(Fe, Mn).sub.3Si.sub.2 phases is counteracted by the aluminum mixed crystals and a rough, block-like formation of the morphology is avoided. In order to set iron (Fe), however, molybdenum is additionally added, which leads to a polygonal morphology and a finer distribution of the Fe intermetallic phases. As a result, the formation of acicular or plate-like -Al.sub.5FeSi phases is suppressed, which phases would occur when there is a high Fe content and a low Mn content (Mn: manganese). The magnesium content is reduced to the extent that, as far as possible, the -Al.sub.8FeMg.sub.3Si.sub.6 phase is not formed. This phase does not dissolve at a solution treatment temperature of 465 C. and would merely set on account of the increased Fe content of the additionally alloyed magnesium (Mg) and lead to skeletal Fe-containing intermetallic phases which are detrimental to ductility in the form of a decrease in the elongation at break and no longer provide for strength-increasing precipitate formation.

[0038] The copper content (Cu content) is used to adjust the required strength in a. targeted manner due to the formation of strength-increasing precipitates during artificial ageing, Nevertheless, it is important to be aware that a copper proportion that is too high during T5 heat treatment leads to embrittlement. The full strength potential of the copper in the alloy can be exploited during T6 heat treatment.

[0039] The addition of titanium (Ti) brings about grain refinement of the aluminum dendrites. A combination with zirconium (Zr) in an adjusted concentration can lead to Al.sub.3(Ti, Zr) precipitates which can have a strength-increasing effect. Care should also be taken at this juncture that titanium and zirconium are not added by alloying in too high a concentration since this leads to an undesirable formation of AlTiZr intermetallic phases which reduce ductility. Adding strontium (Sr) brings about an improvement of the Al/Si eutectic system from coarse and plate-like to an improved, coral-like morphology, thus increasing ductility. This fine Si morphology can be molded quickly and easily by a T6 solution treatment and the ductility can thus be increased once more.

[0040] Production of a component made of an aluminum alloy of this type is described in the following. During production, the above-mentioned aluminum alloy is smelted from master alloys, pure elements or produced by alloying suitable secondary alloys, for example 223 or 226, at a sufficiently high temperature. The alloy is furthermore cast into a temperature-controlled, forced-deaerated or vacuum-deaerated permanent mold. If the casting temperature is too low, there exists a danger of inadequate mold filling and cold running and of undesirable formation of intermetallic phases, whereas casting temperatures that are too high increase the danger of porosity, cavitation and hot cracks. After removing the component produced by casting, the component in order to realize the heat treatment state T6redis cooled in air orin order to realize the heat treatment state T5modis cooled by means of water.

[0041] The special characteristic of the microstructure of the component produced from the aluminum alloy can be seen with reference to FIGS. 1 to 4. FIG. 1 shows a backscatter electron image of the specified secondary alloy 233 comprising copper and molybdenum. Rounded to polygonal molybdenum-containing AlFeMnSi intermetallic phases can be seen. These phases can be found distributed relatively evenly among the Al dendrites in the Al/Si eutectic system since they set concurrently with the system. Due to the small size and rounded morphology of these phases, these increase the ductility of the secondary alloy. The phase Al.sub.8FeMg.sub.3Si.sub.6 can be found sporadically and cannot be dissolved by a solution treatment at 465 C. (cf. FIG. 3). By reducing the Mg content, the formation of this brittle phase can be suppressed and the ductility thus further increased. Potential phases -Al.sub.2Cu and Q-Al.sub.5Cu.sub.2Mg.sub.8Si.sub.6 resulting during solidification should be dissolved by a solution treatment for three hours at 450 C. (cf. FIG. 3) such that the alloy elements Mg and Cu, which are set into these phases, are provided in the Al mixed crystal for precipitate formation.

[0042] FIG. 2 shows a backscatter electron image of the specified secondary alloy 226D (AlSi10Cu3). On account of the high Fe and Mn content, coarse, block-like intermetallic Al.sub.15(Fe, Mn, Cr, Cu).sub.3Si.sub.2 phases are present which, on account of the size thereof, have formed primarily in the casting chamber of the diecasting machine. This accumulation of brittle phases inhibits ductility. Additionally, smaller, polygonal Fe-containing intermetallic phases are present which occur only in the actual diecasting mold. In addition to said Fe-containing intermetallic phases, -Al.sub.5FeSi phases are also present on account of the high Fe content, which phases appear as needles in the two-dimensional microsection surface and in reality are present as three-dimensional plates and therefore as extensive, sharp-edged microstructure divisions between the ductile Al dendrites. These phases reduce ductility significantly. On account of the relatively high content of Ni impurities in this secondary alloy, Al.sub.7Cu.sub.2(Fe, Ni) phases are also formed which cannot be dissolved by a solution treatment at 465 C. and are therefore furthermore present as brittle phases and additionally set Cu (cf. FIG. 4).

[0043] While the alloy is setting, formed Al.sub.2Cu, which is not pronounced in eutectic form AlAl.sub.2CuAl.sub.5Cu.sub.2Mg.sub.8Si.sub.6Si, can be completely dissolved by a solution treatment at 465 C. (cf. FIG. 4), such that, by means of water quenching, the Al mixed crystal is subsequently saturated in Cu. The eutectic pockets AlAl.sub.2CuAl.sub.5Cu.sub.2Mg.sub.8Si.sub.6Si, however, cannot be completely dissolved at 465 C. for three hours. FIGS. 5 and 6 are diagrams for illustrating mechanical properties of components produced from the specified aluminum alloy. Bars 10 illustrate the 0.2% proof stress R.sub.p0.2, whereas bars 12 illustrate the yield point R.sub.m. Triangles 14 illustrate the elongation at break A.sub.5.