Al-Mg-Si-Mn-Fe CASTING ALLOYS

Abstract

New aluminum casting (foundry) alloys are disclosed. The new aluminum casting alloys generally include from 2.5 to 5.0 wt. % Mg, from 0.70 to 2.5 wt. % Si, wherein the ratio of Mg/Si (in weight percent) is from 1.7 to 3.6, from 0.40 to 1.50 wt. % Mn, from 0.15 to 0.60 wt. % Fe, optionally up to 0.15 wt. % Ti, optionally up to 0.10 wt. % Sr, optionally up to 0.15 wt. % of any of Zr, Sc, Hf, V, and Cr, the balance being aluminum and unavoidable impurities. The new aluminum casting alloys may be high pressure die cast, such as into automotive components. The new aluminum alloys may be supplied in an F or a T5 temper, for instance.

Claims

1. An aluminum casting alloy comprising: from 2.5 to 5.0 wt. % Mg; from 0.70 to 2.5 wt. % Si; wherein a weight ratio of magnesium to silicon (wt. % Mg/wt. % Si) is from 1.7:1 to 3.6:1; from 0.40 to 1.5 wt. % Mn; from 0.10 to 0.60 wt. % Fe; optionally up to 0.15 wt. % Ti; optionally up to 0.10 wt. % Sr; optionally up to 0.15 wt. % of any of Zr, Sc, Hf, V, and Cr; the balance being aluminum and unavoidable impurities.

2. The aluminum casting alloy of claim 1, wherein the aluminum casting alloy comprises from 3.0 to 4.60 wt. % Mg.

3. The aluminum casting alloy of claim 2, wherein the aluminum casting alloy comprises from 1.10 to 2.1 wt. % Si.

4. The aluminum casting alloy of claim 3, wherein the aluminum casting alloy comprises from 0.60 to 1.2 wt. % Mn.

5. The aluminum casting alloy of claim 4, wherein the aluminum casting alloy comprises from 0.30 to 0.60 wt. % Fe.

6. The aluminum casting alloy of claim 1, wherein (0.4567*Mg0.5)<=Si<=(0.4567*Mg+0.2).

7. The aluminum casting alloy claim 1, wherein: (1) wt. % Si(0.4567*(wt. % Mg)+0.2*(wt. % Mg)+0.25*(wt. % Fe); and (2) wt. % Si>(0.4567*(wt. % Mg)+0.2*(wt. % Mg)+0.25*(wt. % Fe)-0.6).

8. The aluminum casting alloy of claim 1, wherein the aluminum casting alloy realizes at least one of: an ultimate tensile strength of of at least 200 MPa; a tensile yield strength of at least 110 MPa; and an elongation of at least 10%.

9. The aluminum casting alloy of claim 1, wherein the aluminum casting alloy comprises not greater than 0.012 wt. % of -Al.sub.5FeSi compounds.

10. The aluminum casting alloy of claim 1, wherein the aluminum casting alloy realizes a hot cracking tendency index of not greater than 0.30.

11. A method comprising: (a) shape casting an aluminum casting alloy into a shape cast product, wherein the aluminum casting alloy comprises: from 2.5 to 5.0 wt. % Mg; from 0.70 to 2.5 wt. % Si; wherein a weight ratio of magnesium to silicon (wt. % Mg/wt. % Si) is from 1.7:1 to 3.6:1; from 0.40 to 1.5 wt. % Mn; and from 0.10 to 0.60 wt. % Fe; wherein, after the shape casting, the shape cast product is crack-free; and (b) tempering the shape cast product.

12. The method of claim 11, wherein the shape casting is high-pressure die casting.

13. The method of claim 11, wherein the tempering step comprises tempering the shape cast product to one of an F temper and a T5 temper.

14. The method of claim 11, wherein the tempering step is absent of a solution heat treatment step.

15. The method of claim 11, wherein the shape cast product is in the form of an automotive component.

16. The method of claim 15, wherein the automotive component is a structural component.

17. The method of claim 15, wherein the automotive component is a door frame, or a shock tower, or a tunnel structure.

18. A shape cast aluminum alloy product comprising: from 3.0 to 4.60 wt. % Mg; from 1.20 to 2.0 wt. % Si; wherein a weight ratio of magnesium to silicon (wt. % Mg/wt. % Si) is from 1.85:1 to 3.5:1; from 0.60 to 1.20 wt. % Mn; from 0.20 to 0.60 wt. % Fe; optionally up to 0.15 wt. % Ti; optionally up to 0.10 wt. % Sr; and optionally up to 0.15 wt. % of any of Zr, Sc, Hf, V, and Cr; the balance being aluminum and unavoidable impurities; wherein the shape cast product is in the form of an automotive component.

19. The shape cast aluminum alloy product of claim 18, wherein the automotive component is a structural component.

20. The shape cast aluminum alloy product of claim 18, wherein the automotive component is a door frame, or a shock tower, or a tunnel structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a graph showing silicon content versus hot cracking tendency index for Example 1 alloys.

[0033] FIG. 2 is a graph showing silicon content versus hot cracking tendency index for Example 2 alloys.

[0034] FIG. 3 is a graph showing silicon content versus hot cracking tendency index for Example 3 alloys.

[0035] FIG. 4 is a graph showing manganese content versus hot cracking tendency index for Example 4 alloys.

[0036] FIG. 5a is a graph showing beta phase content (shown in wt. %) as a function of Mn and Fe content based on ICME modeling; the amounts of 3.6 wt. % Mg and 1.5 wt % Si were kept constant.

[0037] FIG. 5b is a graph showing alpha phase content (shown in wt. %) as a function of Mn and Fe content based on ICME modeling; the amounts of 3.6 wt. % Mg and 1.5 wt % Si were kept constant.

[0038] FIG. 6 is a graph showing beta phase content (shown in wt. %) as a function of Fe content based on ICME modeling; the amounts of 3.6 wt. % Mg, 1.5 wt % Si and 0.5 wt. % Mn were kept constant.

[0039] FIG. 7a is a graph showing ultimate tensile strength (MPa) versus iron content (wt. %) for Example 6 alloys.

[0040] FIG. 7b is a graph showing elongtion (%) versus iron content (wt. %) for Example 6 alloys.

[0041] FIG. 7c is a graph showing tensile yield strength (MPa) versus iron content (wt. %) for Example 6 alloys.

[0042] FIG. 7d is a graph showing quality index (Q in MPa) versus iron content (wt. %) for Example 6 alloys.

[0043] FIG. 8a is a graph showing HCI (computed hot cracking index) as a function of Si and Mg content based on ICME modeling; the amounts of 0.70 wt. % Mn and 0.25 wt. % Fe were kept constant.

[0044] FIG. 8b is a graph showing non-equilibrium solidification temperature range (in C.) as a function of Si and Mg content based on ICME modeling; the amounts of 0.70 wt. % Mn and 0.25 wt. % Fe were kept constant.

[0045] FIG. 8c is a graph showing showing HCI (computed hot cracking index) as a function of Si and Mn content based on ICME modeling; the amounts of 4.0 wt. % Mg and 0.25 wt. % Fe were kept constant.

[0046] FIG. 8d is a graph showing showing HCI (computed hot cracking index) as a function of Si and Fe content based on ICME modeling; the amounts of 4.0 wt. % Mg and 0.70 wt. % Mn were kept constant.

DETAILED DESCRIPTION

EXAMPLE 1

[0047] Six aluminum alloys were cast as pencil probe castings. The compositions of the aluminum alloys is given in Table 1, below.

TABLE-US-00001 TABLE 1 Composition of Example 1 Alloys (all values in weight percent) Alloy* Si Fe Mn Mg Ti A1 0.06 0.07 1.24 3.51 0.10 A2 0.75 0.07 1.27 3.59 0.09 A3 1.20 0.10 1.20 3.59 0.09 A4 1.56 0.10 1.20 3.52 0.09 A5 1.88 0.11 1.17 3.69 0.09 A6 2.37 0.08 1.26 3.61 0.09 *The balance of the aluminum alloys was aluminum and unavoidable impurities. The aluminum alloy contained not greater than 0.03 wt. % of any one impurity, and contained not greater than 0.10 wt. %, it total, of all impurities.
Five tests per alloy were conducted and at various connection sizes. Table 2, below, provides the hot cracking results. In the below table, C means cracked during casting, OK means casting was successful without cracking, and NF means the pencil probe mold was not completely filled. The hot cracking tendency index (HCTI) of each alloy was calculated in accordance with the results. Table 2 also lists the calculated HCTI for each alloy.

[0048] The hot cracking tendency index (HCTI) of an alloy is defined as

[00001]$\mathrm{HCTI}=\frac{.Math.\mathrm{diameter}.Math..Math.\mathrm{of}.Math..Math.\mathrm{the}.Math..Math.\mathrm{cracked}.Math..Math.\mathrm{rod}}{\left(4+6+8+10+12+14+16\right)}$

[0049] If no cracking is found on any connection rods, the HCTI value will be 0. If cracking is found in all 7 connection rods (from 4 mm to 16 mm), the HCTI value will be 1. Therefore, a smaller HCTI indicates a higher hot cracking resistance for a specific alloy.

TABLE-US-00002 TABLE 2 Hot Cracking Results of the Example 1 Alloys Connection size Alloy 16 mm 14 mm 12 mm 10 mm 8 mm 6 mm 4 mm HCTI Alloy C C C C C C C 1 A-1 C C C C C C C C C C C C C C C C C C C C C C C C C C C C Alloy OK C OK OK C C OK 0.6 A-2 OK C OK OK C C C OK C C OK OK C C C C OK C C C C C C OK C C OK C Alloy OK OK OK OK OK C OK 0.1 A-3 OK OK OK OK OK C OK OK OK OK OK OK OK C OK OK OK C OK OK OK OK OK OK OK OK OK OK Alloy OK OK OK OK OK OK OK 0.06 A-4 OK OK OK OK OK C OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK C Alloy OK OK OK OK C OK C 0.16 A-5 OK OK OK OK OK OK OK OK OK OK OK C OK C OK OK OK OK C C C OK OK OK OK OK C OK Alloy OK OK OK C C C C 0.39 A-6 OK OK OK OK C C C OK OK OK C C C C OK OK C C C C C OK OK OK OK C C C
FIG. 1 shows a plot of the silicon content versus the determined HCTI value. As shown, alloys having from about 1 to about 2 wt. % Si at similar amounts of Fe, Mn, Mg and Ti realized improved hot cracking resistance. The Mg/Si ratio for these alloys is from about 2.0 to 3.0. Alloy A4 with 1.56 wt. % Si had a Mg to Si ratio of 2.26.

EXAMPLE 2

[0050] Four additional alloys were cast and their hot cracking susceptibility was determined, as per Example 1. Like Example 1, the silicon content was again varied, but using a lower nominal amount of magnesium and manganese. The compositions of the Example 2 alloys are shown in Table 3, below. The HCTI results for the Example 2 alloys are shown in the below figure. Alloy B2 showed the best hot cracking resistance. The Mg/Si ratio for this alloy is about 2.65.

TABLE-US-00003 TABLE 3 Composition of Example 2 Alloys (all values in weight percent) Alloy* Si Fe Mn Mg Ti B1 0.54 0.12 1.12 2.56 0.08 B2 0.96 0.15 1.14 2.54 0.08 B3 1.35 0.15 1.12 2.48 0.08 B4 1.68 0.15 1.11 2.46 0.08 *The balance of the aluminum alloys was aluminum and unavoidable impurities. The aluminum alloy contained not greater than 0.03 wt. % of any one impurity, and contained not greater than 0.10 wt. %, it total, of all impurities.

[0051] FIG. 2 shows the experimental measured hot cracking tendency indexes of the Al2.5Mg-1.1Mn-x % Si alloys. Alloy B2, with 0.96 wt. % Si and 2.54 wt. % Mg, showed the best ho cracking resistance. The Mg/Si ratio for this alloy is about 2.65.

EXAMPLE 3

[0052] Four additional alloys were cast and their hot cracking susceptibility was determined, as per Example 1. Like Example 1, the silicon content was again varied, but using a higher nominal amount of magnesium and a lower nominal amount of manganese. The compositions of the Example 3 alloys are shown in Table 4, below. The HCTI results for the Example 3 alloys are shown in FIG. 3. As shown, the HCTI for all alloys is generally good. The lowest HCTI was realized by alloy C3 with a Mg/Si ratio of 2.22.

TABLE-US-00004 TABLE 4 Composition of Example 3 Alloys (all values in weight percent) Alloy* Si Fe Mn Mg Ti Mg/Si C1 1.31 0.14 0.95 4.55 0.08 3.48 C2 1.57 0.15 0.92 4.51 0.08 2.87 C3 2.00 0.15 0.91 4.43 0.08 2.22 C4 2.40 0.15 0.91 4.35 0.08 1.81 *The balance of the aluminum alloys was aluminum and unavoidable impurities. The aluminum alloy contained not greater than 0.03 wt. % of any one impurity, and contained not greater than 0.10 wt. %, it total, of all impurities.

[0053] The results of Examples 1-3 indicate that the Mg/Si (weight ratio) should be from about 1.7 to about 3.6, preferably from about 2.0 to about 3.0 to facilitate hot cracking resistance.

EXAMPLE 4

[0054] Four additional alloys were cast and their hot cracking susceptibility was determined, as per Example 1. This time, the manganese content was varied, targeting a nominal magnesium amount of 3.6 wt. % and a nominal silicon amount of 1.5 wt. %. The compositions of the Example 4 alloys are shown in Table 5, below. The HCTI results for the Example 4 alloys are shown in FIG. 4. As shown, the HCTI for all alloys is generally good. Alloy D4 with 1.20 wt. % Mn realized the best HCTI results.

TABLE-US-00005 TABLE 5 Composition of Example 4 Alloys (all values in weight percent) Alloy* Si Fe Mn Mg Ti Mg/Si D1 1.52 0.11 0.47 3.64 0.08 2.39 D2 1.53 0.14 0.81 3.66 0.08 2.39 D3 1.53 0.13 1.09 3.58 0.08 2.34 D4 1.53 0.13 1.20 3.57 0.08 2.33 *The balance of the aluminum alloys was aluminum and unavoidable impurities. The aluminum alloy contained not greater than 0.03 wt. % of any one impurity, and contained not greater than 0.10 wt. %, it total, of all impurities.

EXAMPLE 5

[0055] Four additional alloys were cast and their hot cracking susceptibility was determined, as per Example 1. This time, the iron content was varied, targeting a nominal magnesium amount of 3.45 wt. %, a nominal silicon amount of 1.55 wt. %, and a nominal manganese amount of 0.90 wt. %. The compositions of the Example 5 alloys are shown in Table 6, below. The HCTI results for the Example 5 alloys are shown in the below figure. As shown, the HCTI for all alloys is generally good. Alloy E4 with 0.29 wt. % Fe realized the best HCTI results.

TABLE-US-00006 TABLE 6 Composition of Example 5 Alloys (all values in weight percent) Alloy* Si Fe Mn Mg Ti Mg/Si E1 1.54 0.11 0.83 3.46 0.07 2.25 E2 1.55 0.17 0.85 3.46 0.07 2.23 E3 1.55 0.23 0.90 3.44 0.07 2.22 E4 1.55 0.29 0.94 3.45 0.07 2.23 *The balance of the aluminum alloys was aluminum and unavoidable impurities. The aluminum alloy contained not greater than 0.03 wt. % of any one impurity, and contained not greater than 0.10 wt. %, it total, of all impurities.

[0056] These results are unexpected. The mechanical properties of AlSi foundry alloys are adversely affected by iron because the iron is present as large primary or pseudo-primary compounds which increase the hardness but decrease the ductility. Given these improved HCTI results, modeling was conducted (ICMEIntegrated Computational Materials Engineering). These results show that, by controlling Fe and Mn contents, formation of unwanted needle-shaped -Al.sub.5FeSi can be potentially avoided. FIGS. 5a, 5b and 6 show the correlation between manganese and iron content and the volume fraction on -Al.sub.5FeSi and -Al.sub.15FeMn.sub.3Si.sub.2 phase particles (for a Al -3.6Mg-1.5Si alloys). Adding Mn to the AlMgSi alloys can promote formation of -Al.sub.15FeMn.sub.3Si.sub.2 phase and restrict or prevent formation of -Al.sub.5FeSi phase. For instance, a Al-3.6Mg-1.5Si alloy with from 0.4 to 0.6 wt. % Mn, using increased iron amounts decreases the amount of -Al.sub.5FeSi phase. As shown in FIG. 6, the amount of -Al.sub.5FeSi phase decreases from about 0.018 wt. % to essentially 0 wt. % by increasing iron from 0.15 wt. % to 0.4 wt. %. Thus, alloys having improved properties (e.g., elongation) may be realized due to the increase in iron and the corresponding decrease in -Al.sub.5FeSi phase within the alloy.

EXAMPLE 6

[0057] Eight additional alloys were cast via directional solidification. All alloys varied iron content. The first group (F) targeted a nominal magnesium amount of 3.6 wt. %, a nominal silicon amount of 1.5 wt. %, and a nominal manganese amount of 0.90 wt. %. The second group (G) targeted a nominal magnesium amount of 4.0 wt. %, a nominal silicon amount of 1.7 wt. %, and a nominal manganese amount of 0.65 wt. %. The compositions of the Example 6 alloys are shown in Table 7, below.

TABLE-US-00007 TABLE 6 Composition of Example 5 Alloys (all values in weight percent) Alloy* Si Fe Mn Mg Ti Mg/Si F1 1.53 0.12 0.93 3.61 0.08 2.36 F2 1.55 0.19 0.93 3.63 0.08 2.34 F3 1.56 0.27 0.93 3.63 0.08 2.33 F4 1.53 0.38 0.93 3.60 0.08 2.35 G1 1.72 0.12 0.65 4.01 0.08 2.33 G2 1.73 0.19 0.64 4.03 0.08 2.33 G3 1.73 0.29 0.64 4.02 0.08 2.33 G4 1.73 0.40 0.64 4.00 0.08 2.32 *The balance of the aluminum alloys was aluminum and unavoidable impurities. The aluminum alloy contained not greater than 0.03 wt. % of any one impurity, and contained not greater than 0.10 wt. %, it total, of all impurities.

[0058] The mechanical properties of the directionally solidified alloys were tested in accordance with ASTM E8 and B557, the results of which are provided in Table 7, below. The mechanical properties of the Example 5 alloys were also tested, so those results are also included in Table 7. The quality index (Q) is also provided. (Q=UTS+150*log(Elong.)). Various graphs relating to these properties and the alloy compositions are provided in FIGS. 7a-7d.

TABLE-US-00008 TABLE 7 Properites of Alloys E1-E4, F1-F4 and G1-G4 Mechanical Property Average UTS, TYS, Elong., Q, STDEV Alloy MPa MPa % MPa UTS TYS Elong. Q E1 226 104 9.0 369 12.1 6.0 0.7 15.2 E2 224 109 7.3 353 10.3 4.1 1.2 14.6 E3 233 105 9.2 377 6.4 6.2 0.5 9.0 E4 232 106 10.6 385 8.1 2.3 2.3 20.0 F1 212 112 13.8 382 6.7 4.0 1.7 13.5 F2 212 112 13.8 382 5.6 3.0 2.1 11.8 F3 214 113 16.0 394 7.1 3.5 1.4 11.1 F4 209 116 11.5 365 0.5 5.0 4.0 23.7 G1 211 114 12.5 375 7.5 4.1 1.0 11.2 G2 211 113 12.8 376 8.0 2.6 2.4 19.3 G3 215 126 11.3 372 4.9 4.2 1.5 9.7 G4 212 113 14.0 384 5.0 8.2 1.6 6.6

EXAMPLE 7

Experimental Modeling

[0059] Based on the prior experiments, various aluminum alloy compositions were modeled. The results are shown in FIGS. 8a-8b. These modeling results indicate that for an AlMgSi alloy targeting 0.7 wt. % Mn and 0.25 wt. % Fe, it may be useful to control the magnesium and silicon such that (all values in weight percent): (0.4567*Mg0.5)<=Si<=(0.4567*Mg+0.2)

[0060] Similar modeling was done on additional aluminum alloys, as shown in FIGS. 8c-8d. These modeling results indicate that, as the manganese or iron content increases, the silicon content needs to be increased. These results further indicate that it may be useful to control magnesium, silicon, manganese, and iron as per the following:

[0061] (0.4567*Mg+0.2*Mn+0.25*Fe0.6)<=Si<=(0.4567*Mg+0.2*Mn+0.25*Fe)

[0062] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure.