3XX aluminum casting alloys, and methods for making the same

Abstract

New 3xx aluminum casting alloys are disclosed. The aluminum casting alloys generally include from 6.5 to 11.0 wt. % Si, from 0.20 to 0.80 wt. % Mg, from 0.05 to 0.50 wt. % Cu, from 0.10 to 0.80 wt. % Mn, from 0.005 to 0.05 wt. % Sr, up to 0.25 wt. % Ti, up to 0.30 wt. % Fe, and up to 0.20 wt. % Zn, the balance being aluminum and impurities.

Claims

1. A 3xx aluminum alloy shape cast product, consisting of: 6.5-8.9 wt. % Si; 0.55-0.80 wt. % Mg; 0.15-0.35 wt. % Cu; 0.30-0.80 wt. % Mn; 0.012-0.040 wt. % Sr; up to 0.25 wt. % Ti; up to 0.12 wt. % Fe; and up to 0.20 wt. % Zn; the balance being aluminum (Al) and impurities, wherein the 3xx aluminum alloy shape cast product includes not greater than 0.10 wt. % of any one impurity, and wherein the 3xx aluminum alloy shape cast product includes not greater than 0.35 wt. %, in total, of the impurities; wherein the 3xx aluminum alloy shape cast ptoduct realizes a quality index of at least 400; wherein the 3xx aluminum alloy shape cast product is absent of die soldering defects; and wherein the 3xx aluminum alloy shape cast product includes a suffocoent amount of the Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities to achieve a tensile yield strenght of at least 290 MPa and when tested in accordance with ASTM E8 and B557.

2. The 3xx aluminum alloy shape cast product of claim 1, having at least 7.25 wt. % Si.

3. The 3xx aluminum alloy shape cast product of claim 1, having at least 8.0 wt. % Si.

4. The 3xx aluminum alloy shape cast product of claim 1, having not greater than 0.75 wt. % Mg.

5. The 3xx aluminum alloy cast product of claim 1, having not greater than 0.70 wt. % Mg.

6. The 3xx aluminum alloy shape cast product of claim 1, having at least 0.18 wt. % Cu.

7. The 3xx aluminum alloy shape cast product of claim 1, having at least 0.35 wt. % Mn.

8. The 3xx aluminum alloy shape cast product of claim 1, having not greater than 0.65 wt. % Mn.

9. The 3xx aluminum alloy shape cast product of claim 1, having from 0.005 to 0.25 wt. % Ti.

10. The 3xx aluminum alloy shape cast product of claim 1, having not greater than 0.11 wt. % Fe and not greater than 0.15 wt. % Zn.

11. The 3xx aluminum alloy shape cast product of claim 1, wherein the 3xx aluminum alloy shape cast product includes a sufficient amount of the Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities to achieve an elongation of at least 5% when tested in accordance with ASTM E8 and B557.

12. The 3xx aluminum alloy shape cast product of claim 1, wherein the 3xx aluminum alloy shape cast product includes a sufficient amount of the Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities to achieve a quality index of at least 430.

13. The 3xx aluminum alloy shape cast product of claim 1, having at least 0.60 wt. % Mg.

14. The 3xx aluminum alloy shape cast product of claim 1, having at least 0.40 wt. % Mn.

15. The 3xx aluminum alloy shape cast product of claim 1, having at least 0.45 wt. % Mn.

16. The 3xx aluminum alloy shape cast product of claim 1, wherein the 3xx aluminum alloy shape cast product includes a sufficient amount of the Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities to achieve an elongation of at least 6% when tested in accordance with ASTM E8 and B557.

17. The 3xx aluminum alloy shape cast product of claim 1, wherein the 3xx aluminum alloy shape cast product is an automotive component.

18. The 3xx aluminum alloy shape cast product of claim 17, wherein the shape cast product is a shape cast body-in-white part or a shape cast suspension part.

19. The 3xx aluminum alloy shape cast product of claim 1, wherein the 3xx aluminum alloy shape cast product has a wall thickness of from 2 to 5 mm.

20. The 3xx aluminum alloy shape cast product of claim 1, wherein the 3xx aluminum alloy shape cast product comprises a sufficient amount of alloying elements of Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities to achieve an intergranular corrosion resistance that is comparable to the intergranular corrosion resistance of a baseline shaped cast part, wherein the baseline shaped cast part is made from conventional alloy A365, and wherein the intergranular corrosion resistance is tested in accordance with ASTM G110-92 (2015), measured on the as-cast shape cast part (not machined) after 24 hours of exposure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 provides various embodiments of the new 3xx aluminum casting alloys.

(2) FIG. 2 shows ASTM G110 corrosion data for various Example 1 alloys.

(3) FIGS. 3a-3c are graphs showing various properties of the Example 2 alloys.

(4) FIGS. 4a-4c are graphs showing the effect of copper, magnesium and silicon relative to the Example 2 alloys.

(5) FIG. 5 is a graph showing the staircase fatigue results of Example 3.

DETAILED DESCRIPTION

EXAMPLE 1

(6) Several 3xx aluminum casting alloys having the compositions shown in Table 1, below, were cast via directional solidification (DS). The dimensions of the directionally solidified alloys were approximately 25.4 mm (1 inch) thick, 102 mm (4 inches) wide, and 254 mm (10 inches) long.

(7) TABLE-US-00001 TABLE 1 Composition of Example 1 Alloys (in wt. %) Alloy** Si Fe Cu Mn Mg Sr A1 8.59 0.11 — 0.51 0.55 0.012 A2* 8.48 0.11 0.20 0.50 0.54 0.012 A3 8.60 0.11 0.51 0.51 0.54 0.018 *Invention alloy **All alloys contained TiB.sub.2 as a grain refiner, and about 0.010-0.020 wt. % Ti; the balance of the alloys was aluminum and unavoidable impurities, with the alloys containing not greater than 0.03 wt. % of any one unavoidable impurity, and not greater than 0.10 wt. % total of the unavoidable impurities; the alloys contained not greater than 0.03 wt. % Zn.

(8) After casting, the alloys were solution heated and then quenching in cold water. After holding for 12-24 hours, various specimens from the alloys were artificially aged at 190° C. (374° F.) for various times. Strength testing in accordance with ASTM B557-10 was then conducted, the results of which are provided in Table 2, below (all values the average of at least triplicate specimens).

(9) TABLE-US-00002 TABLE 2 Mechanical Properties of Alloys A1-A3 Aging Time TYS UTS Elong. Alloy (hrs. @ 190° C.) (MPa) (MPa) (%) A1 (0 Cu) 1 278.4 324.8 7.3 A1 (0 Cu) 2 285.0 322.8 4.3 A1 (0 Cu) 4 277.6 310.0 4.0 A2 (0.20% Cu) 1 291.3 341.3 6.3 A2 (0.20% Cu) 2 298.1 338.6 4.5 A2 (0.20% Cu) 4 289.8 323.0 3.8 A3 (0.51% Cu) 1 285.5 350.0 6.4 A3 (0.51% Cu) 2 294.8 346.2 5.7 A3 (0.51% Cu) 4 286.0 324.9 4.8

(10) As shown, peak strength was achieved by artificial aging at 190° C. for 2 hours for all three alloys. Adding 0.2 wt. % Cu increased peak yield strength by 13 MPa, whereas adding 0.51 wt. % Cu only increases peak yield strength by 10 MPa. Elongation decreases with increasing aging time.

(11) The corrosion resistance of the alloys aged at 190° C. for 2 hours was also evaluated in accordance with ASTM G110 (2009), entitled “Standard Practice for Evaluating Intergranular Corrosion Resistance of Heat Treatable Aluminum Alloys by Immersion in Sodium Chloride+Hydrogen Peroxide Solution”. Corrosion mode and depth-of-attack on both the as-cast surface and machined surface were assessed. The depth of attack results are shown in FIG. 2. Increasing Cu content from 0.20 wt. % to 0.51 wt. % increased the depth-of-attack by 30 to 40%.

EXAMPLE 2

(12) Several 3xx aluminum casting alloys having the compositions shown in Table 3, below, were cast via directional solidification (DS). The dimensions of the directionally solidified alloys were approximately 25.4 mm (1 inch) thick, 102 mm (4 inches) wide, and 254 mm (10 inches) long.

(13) TABLE-US-00003 TABLE 3 Composition of Example 2 Alloys Alloy* Si Mg Cu Mn Fe Sr B1 8.91 0.65 0.11 0.55 0.10 0.013 B2 8.76 0.65 0.26 0.54 0.09 0.013 B3 8.76 0.65 0.34 0.54 0.09 0.013 B4 8.81 0.62 0.44 0.54 0.09 0.007 B5 8.22 0.39 0.19 0.52 0.10 0.014 B6 8.10 0.55 0.18 0.50 0.10 0.014 B7 8.14 0.74 0.18 0.50 0.10 0.014 B8 5.49 0.55 0.22 0.55 0.10 0.017 B9 6.91 0.53 0.21 0.54 0.11 0.016 B10 8.18 0.54 0.19 0.50 0.10 0.012 B11 9.52 0.53 0.19 0.50 0.10 0.012 B12 10.86 0.52 0.20 0.50 0.11 0.013 *All alloys contained TiB.sub.2 as a grain refiner, and about 0.010-0.020 wt. % Ti; the balance of the alloys was aluminum and unavoidable impurities, with the alloys containing not greater than 0.03 wt. % of any one unavoidable impurity, and not greater than 0.10 wt. % total of the unavoidable impurities; the alloys contained not greater than 0.03 wt. % Zn.

(14) After casting, the alloys were solution heated and then quenching in cold water. After holding for 12-24 hours, various specimens from the alloys were artificially aged at 190° C. (374° F.) for various times. Mechanical properties of the artificially aged materials were then tested (duplicate specimens at two locations of each casting for each aging condition), the results of which are shown in Tables 4-6, below (average and standard deviation of the four total specimens per cast and per aging condition). The quality index is shown in Table 7 (QI=UTS(MPa)+150*log(Elongation). The mechanical properties of alloy B1 had a large standard deviation and were inconsistent with other alloy testing, so those tests were excluded.

(15) TABLE-US-00004 TABLE 4 Tensile Yield Strength Average Alloy 1 hr @ 190 C. 2 hr @ 190 C. 4 hr @ 190 C. B1 N/A N/A N/A B2 273.2 295.4 299.7 B3 274.7 277.8 277.3 B4 263.9 273.5 274.4 B5 267.2 267.5 260.6 B6 272.7 275.3 275.3 B7 272.8 274.4 272.5 B8 271.1 282.0 276.3 B9 280.4 287.3 283.9 B10 279.6 281.8 271.8 B11 268.5 270.4 268.0 B12 266.5 268.4 267.7

(16) TABLE-US-00005 TABLE 5 Ultimate Tensile Strength Average Alloy 1 hr @ 190 C. 2 h r@ 190 C. 4 hr @ 190 C. B1 N/A N/A N/A B2 321.6 328.8 318.1 B3 325.7 319.4 310.9 B4 319.5 320.2 312.5 B5 321.4 311.8 296.3 B6 323.7 313.7 313.7 B7 317.1 310.1 300.2 B8 288.3 299.9 289.7 B9 321.6 319.0 308.8 B10 331.8 320.7 303.2 B11 316.6 311.4 304.0 B12 319.5 312.8 308.0

(17) TABLE-US-00006 TABLE 6 Elongation Average Alloy 1 hr @ 190 C. 2 hr @ 190 C. 4 hr @ 190 C. B1 N/A N/A N/A B2 9.8 4.4 4.3 B3 11.5 8.7 7.9 B4 10.6 6.2 4.3 B5 11.5 6.8 5.5 B6 9.8 6.4 5.2 B7 8.8 4.1 3.3 B8 2.2 0.6 0.8 B9 5.2 2.7 2.3 B10 8.7 4.4 3.0 B11 7.1 5.5 3.9 B12 8.8 5.9 8.0

(18) TABLE-US-00007 TABLE 7 Quality Index Average Alloy 1 hr @ 190 C. 2 hr @ 190 C. 4 hr @ 190 C. B1 N/A N/A N/A B2 470.3 425.3 413.1 B3 484.8 460.3 445.5 B4 473.3 439.1 407.5 B5 480.5 436.7 407.4 B6 472.4 434.6 421.1 B7 458.8 402.0 378.0 B8 339.7 266.6 275.2 B9 429.0 383.7 363.1 B10 472.7 417.2 374.8 B11 444.3 422.5 392.7 B12 461.2 428.4 443.5

(19) As shown, all alloys, except Alloy B8, realize an excellent combination of strength and ductility. Thus, alloys B2-B7 and B9-B12 of Example 2 are considered invention alloys. Of these, the alloys having about 0.2-0.4 wt. % Cu and about 0.5-0.7 wt. % Mg are better performing (alloys B2-B3, B4, B6, and B9-12). Alloys B2-B3 and B10, with 8.16-8.76 wt. % Si, 0.54-0.65 wt. % Mg, and 0.19-0.34 wt. % Cu, tend to realize the best combination of strength and elongation.

EXAMPLE 3

(20) Several cast nodes (approx. 30) were high pressure die cast for an automotive frame structure on a 1350-tonne vacuum-assisted HPDC machine. The average measured composition is provided in Table 8, below. The cast nodes showed no die sticking and no hot cracking. The invention alloy showed good fluidity, completely filling the 2-5 mm thin wall casting part; zero non-fill issues were identified.

(21) TABLE-US-00008 TABLE 8 Composition of Example 3 Alloy* Cu Mg Si Fe Mn Sr 0.19 0.60 8.85 0.17 0.42 0.017 *The alloy contained TiB.sub.2 as a grain refiner, and about 0.05 wt. % Ti; the balance of the alloys was aluminum and unavoidable impurities, with the alloys containing not greater than 0.03 wt. % of any one unavoidable impurity, and not greater than 0.10 wt. % total of the unavoidable impurities; the amount of zinc in the alloy was not greater than 0.03 wt. % Zn.

(22) After casting, the materials were solution heat treated, quenched and processed to the T6 temper by artificially aging at 180° C. (356° F.) for 4 hours. Tensile specimens were taken from different locations of one cast node, and tensile tests were performed per ASTM Method B557-10. Table 2 shows the tensile results. The average yield strength is 300 MPa, and average elongation is 8.3%.

(23) TABLE-US-00009 TABLE 9 Mechanical Properties of a Cast Node Yield Tensile Specimen Thickness, Strength, Strength, Elongation, ID mm Mpa Mpa % 1 3.47 295 360.5 10 2 2.8 302.5 364.5 10 3 3.09 296.5 360.5 10 4 2.73 311.5 367.5 10 5 2.87 298.5 347.5 6 6 3.3 304.5 353 6 7 1.1 298.5 348 6 8 2.55 300.5 358 6 9 5.59 295 357 10 10 4.61 300 359 10 11 3.34 302 356 10 12 2.73 300.5 356 6 Average 3.18 300.4 357.3 8.33

(24) Tensile tests were also performed for the incumbent A365 alloy using the castings made on the same HPDC machine using the same casting process, solution heat treatment and artificial aging practice. The average mechanical properties achieved for the A365 alloy were 247 MPa yield strength, 309MPa tensile strength and 8.7% elongation. The invention alloy, therefore, realizes about 20% higher yield strength than the conventional A365 alloy while maintaining similar elongation.

(25) Welding tests and corrosion tests were also conducted on an invention alloy cast node and conventional alloy A365 cast node. The alloys were welded to conventional 6082 extruded rod using gas metal arc welding (GMAW). Good quality welds between the invention alloy cast node and the 6082 extruded rod were obtained, with no substantive cracks or discontinuity in the weld zone. Corrosion resistance testing per ASTM G110 were conducted on the bare and welded materials, the results of which are shown in Table 10, below. As shown, the invention alloy realizes comparable corrosion resistance to that of conventional alloy A365, realizing similar types of attack.

(26) TABLE-US-00010 TABLE 10 Depth of Attack in 24 Hour ASTM G110 Depth of attack (Microns) Type of Location Alloy site 1 site 2 site3 site4 site5 Max. Ave. Attack Base 6082-T6 27 4 4 4 4 27 8.6 Pitting Base Invention- 323 254 246 244 242 323 261.8 pitting + inter- T6 dendritic Base A365-T6 191 189 187 164 164 191 179.2 pitting + inter- dendritic Invention- Invention- 166 158 106 83 83 166 123.0 Pitting + inter- 6082 weld T6 near dendritic weld 6082-T6 19 19 19 14 14 19 17.4 pitting near weld A365- A365-T6 220 141 133 126 118 220 147.6 Pitting + inter- 6082 weld near weld dendritic 6082-T6 24 17 12 9 8 24 14.0 pitting near weld

(27) Fatigue specimens were machined from an invention alloy cast node, and staircase fatigue testing in accordance with ASTM E466-15 was completed. Conventional alloy A365, also in the T6 temper, was also tested. Axial fatigue specimens were machined from HPDC brackets with wall thickness around 3 mm. Testing was conducted at room temperature in load control on servo-hydraulic test equipment employing a sinusoidal waveform operating at a test frequency 50 hertz. An R-Ratio of −1 was used with a run-out of 10,000,000 cycles. Any test reaching 10,000,000 cycles was discontinued.

(28) The general test procedure is as follows: If a test reaches the desired cycle count, the next test is started at a higher stress level. If a test does not reach the desired cycle count, the next test is started at a lower stress level. This continues until the required number of tests is complete. The stress level adjustment is constant and is referred to as the step size.

(29) The fatigue strength results are shown in FIG. 5 and Table 11, below. As shown, the invention alloy realizes significantly better fatigue life than the comparison alloy, approximately 21.4% better ((116.25−95.75)/95.75)=21.4%) in the case of the invention alloy cast node.

(30) TABLE-US-00011 TABLE 11 Fatigue Strength Results Invention Alloy Cast Node A365-T6 Cast Node Specimen Cycles to Cycles to # Stress, MPa Failure Stress, MPa Failure 1 90 10,000,000 90.0 10,000,000 2 95 10,000,000 95.0 376,441 3 100 8,301,498 90.0 10,000,000 4 95 10,000,000 95.0 704,513 5 100 10,000,000 90.0 10,000,000 6 105 10,000,000 95.0 1,108,396 7 110 10,000,000 92.5 330,998 8 115 10,000,000 90.0 10,000,000 9 120 2,382,300 92.5 10,000,000 10 115 10,000,000 95.0 10,000,000 11 120 674,721 97.5 1,476,699 12 115 1,600,767 95.0 10,000,000 13 110 10,000,000 97.5 10,000,000 14 115 10,000,000 100.0 3,912,394 15 120 7,324,559 97.5 10,000,000 16 115 10,000,000 100.0 560,092 17 120 544,491 97.5 593,273 18 115 10,000,000 95.0 10,000,000 19 120 10,000,000 97.5 10,000,000 20 125 10,000,000 100.0 510,622 21 130 1,364,893 97.5 1,074,440 22 125 182,926 95.0 10,000,000

(31) While various embodiments of the new technology described herein 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 presently disclosed technology.