3XX ALUMINUM CASTING ALLOYS, AND METHODS FOR MAKING THE SAME
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.
This application is a continuation of U.S. patent application Ser. No. 15/895,497, filed Feb. 13, 2018, which is a continuation of International Patent Application No. PCT/US2016/046613, filed Aug. 11, 2016, which claims the benefit of priority of U.S. Provisional Patent Application No. 62/204,762, filed Aug. 13, 2015, both entitled “IMPROVED 3 XX ALUMINUM CASTING ALLOYS, AND METHODS FOR MAKING THE SAME” each of which is incorporated herein by reference in its entirety.
BACKGROUNDAluminum alloys are useful in a variety of applications. However, improving one property of an aluminum alloy without degrading another property is elusive. For example, it is difficult to increase the strength of an aluminum casting alloy without affecting other properties such as castability and ductility. See, for example, U.S. Pat. No. 6,773,666.
SUMMARYBroadly, the present patent application relates to improved 3 xx aluminum casting alloys, and methods for producing the same. The new 3 xx aluminum casting alloys generally comprise (and in some instance consist essentially of, or consist of), 6.5-11.0 wt. % Si (silicon), 0.20-0.80 wt. % Mg (magnesium), 0.05-0.50 wt. % Cu (copper), 0.10-0.80 wt. % Mn (manganese), 0.005-0.050 wt. % Sr (strontium), up to 0.25 wt. % Ti (titanium), up to 0.30 wt. % Fe (iron), up to 0.20 wt. % Zn (zinc), the balance being aluminum (Al) and impurities.
Regarding silicon, the new 3 xx aluminum casting alloys generally include from 6.5 to 11.0 wt. % Si. In one embodiment, a new 3 xx aluminum casting alloy includes at least 7.0 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes at least 7.25 wt. % Si. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 7.5 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes at least 7.75 wt. % Si. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 8.0 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes at least 8.25 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes at least 8.40 wt. % Si. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 8.50 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes at least 8.60 wt. % Si. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 10.75 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 10.5 wt. % Si. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 10.25 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 10.0 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 9.75 wt. % Si. In another embodiment, anew 3 xx aluminum casting alloy includes not greater than 9.50 wt. % Si. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 9.25 wt. % Si. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 9.00 wt. % Si. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 8.90 wt. % Si.
The new 3 xx aluminum casting alloys generally include magnesium in the range of from 0.20 to 0.80 wt. % Mg. In one embodiment, a new 3 xx aluminum casting alloy includes at least 0.30 wt. % Mg. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.40 wt. % Mg. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 0.45 wt. % Mg. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.50 wt. % Mg. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 0.55 wt. % Mg. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.60 wt. % Mg. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.75 wt. % Mg. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.725 wt. % Mg. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.70 wt. % Mg. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.675 wt. % Mg. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.65 wt. % Mg.
The new 3 xx aluminum casting alloys generally include copper and in the range of from 0.05 to 0.50 wt. % Cu. As shown below, use of copper may facilitate, for example, improved strength. Too much copper may unacceptably degrade corrosion resistance. In one embodiment, a new 3 xx aluminum casting alloy includes at least 0.075 wt. % Cu. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.10 wt. % Cu. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 0.125 wt. % Cu. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.15 wt. % Cu. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 0.18 wt. % Cu. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.45 wt. % Cu. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.40 wt. % Cu. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.35 wt. % Cu. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.30 wt. % Cu. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.25 wt. % Cu.
The new 3 xx aluminum casting alloys generally include from 0.10 to 0.80 wt. % Mn. As shown below, manganese may facilitate, for example, improved die sticking resistance (sometimes called die soldering resistance), which can be problematic when casting via high-pressure die casting. In one embodiment, a new 3 xx aluminum casting alloy includes at least 0.15 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.20 wt. % Mn. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 0.25 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.30 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.35 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.40 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.45 wt. % Mn. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.75 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.70 wt. % Mn. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.65 wt. % Mn. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.60 wt. % Mn.
The new 3 xx aluminum casting alloys generally include from 0.005 (50 ppm) to 0.050 wt. % (500 ppm) Sr. Strontium modifies the aluminum-silicon eutectic. In one embodiment, a new 3 xx aluminum casting alloy includes at least 0.008 wt. % Sr. In another embodiment, a new 3 xx aluminum casting alloy includes at least 0.010 wt. % Sr. In yet another embodiment, a new 3 xx aluminum casting alloy includes at least 0.012 wt. % Sr. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.040 wt. % Sr. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.030 wt. % Sr. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.025 wt. % Sr. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.022 wt. % Sr. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.020 wt. % Sr. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.018 wt. % Sr. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.016 wt. % Sr. In some instances, sodium and/or antimony may be used as a substitute (in whole or in part) for strontium.
The new 3 xx aluminum casting alloys may include up to 0.25 wt. % titanium. Titanium may facilitate grain refining. In embodiments where titanium is present, the new 3 xx aluminum casting alloys generally include from 0.005 to 0.25 wt. % Ti. In one embodiment, the new 3 xx aluminum casting alloys includes from 0.005 to 0.20 wt. % Ti. In one embodiment, the new 3 xx aluminum casting alloys includes from 0.005 to 0.15 wt. % Ti. When used, the appropriate amount of titanium can be readily selected by those skilled in the art. See, ASM International Metal Handbook, Vol. 15, Casting (1988), pp. 746 and 750-751, which is incorporated herein by reference in its entirety. In some embodiments, the new 3 xx aluminum casting alloys are substantially free of titanium, and, in these embodiments, contain less than 0.005 wt. % Ti (e.g., in some high-pressure die casting operations).
The new 3 xx casting alloys may include up to 0.30 wt. % Fe. Excess iron may detrimentally impact ductility. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.25 wt. % Fe. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.20 wt. % Fe. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.15 wt. % Fe. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.14 wt. % Fe. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.13 wt. % Fe. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.12 wt. % Fe. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.11 wt. % Fe. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.10 wt. % Fe. The new 3 xx aluminum casting alloy generally include at least 0.01 wt. % Fe.
The new 3 xx casting alloys may include up to 0.20 wt. % Zn as an impurity Excess zinc may detrimentally impact properties. However, some zinc may be inevitable as an unavoidable impurity. In one embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.15 wt. % Zn. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.10 wt. % Zn. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.07 wt. % Zn. In another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.05 wt. % Zn. In yet another embodiment, a new 3 xx aluminum casting alloy includes not greater than 0.03 wt. % Zn. In some of the embodiments, the new 3 xx aluminum casting alloy may include at least 0.01 wt. % Zn.
The remainder of the new 3 xx aluminum casting alloy generally comprises aluminum and impurities (“impurities” means all unavoidable impurities except iron and zinc, which are described above and have their own individual limits). Generally, the new 3 xx aluminum casting contains not more than 0.10 wt. % each of impurities, with the total combined amount of the impurities not exceeding 0.35 wt. %. In another embodiment, each one of the impurities, individually, does not exceed 0.05 wt. % in the new 3 xx aluminum casting alloys, and the total combined amount of the impurities does not exceed 0.15 wt. % in the new 3 xx aluminum casting alloys. In another embodiment, each one of the impurities, individually, does not exceed 0.04 wt. % in the new 3 xx aluminum casting alloys, and the total combined amount of the impurities does not exceed 0.12 wt. % in the new 3 xx aluminum casting alloys. In another embodiment, each one of the impurities, individually, does not exceed 0.03 wt. % in the new 3 xx aluminum casting alloys, and the total combined amount of the impurities does not exceed 0.10 wt. % in the new 3 xx aluminum casting alloys.
In one approach, a new 3 xx aluminum casting alloy consists of 8.0-9.5 wt. % Si, 0.20-0.80 wt. % Mg, 0.15-0.50 wt. % Cu, 0.10-0.80 wt. % Mn, 0.005-0.025 wt. % Sr, up to 0.20 wt. % Ti, up to 0.20 wt. % Fe, and up to 0.10 wt. % Zn, and the balance being aluminum (Al) and impurities, wherein the aluminum casting alloy includes not greater than 0.05 wt. % of any one impurity, and wherein the aluminum casting alloy includes not greater than 0.15 wt. %, in total, of the impurities. In one embodiment, this new 3 xx aluminum casting alloy consists of 8.4-9.0 wt. % Si, 0.60-0.80 wt. % Mg, 0.18-0.25 wt. % Cu, 0.35-0.45 wt. % Mn, 0.015-0.020 wt. % Sr, up to 0.15 wt. % Ti, up to 0.12 wt. % Fe, and up to 0.07 wt. % Zn, the balance being aluminum (Al) and impurities, wherein the aluminum casting alloy includes not greater than 0.04 wt. % of any one impurity, and wherein the aluminum casting alloy includes not greater than 0.12 wt. %, in total, of the impurities. In one, a high pressure die casting made from such 3 xx aluminum casting alloys realizes a tensile yield strength of at least 280 MPa, an elongation of at least 6%, and a Quality Index (QI) of at least 400 in the T6 temper.
In one embodiment, the new 3 xx aluminum casting alloy is cast into a 3 xx shape cast part/product. In this regard, the casting step may be high pressure die casting (e.g., vacuum assisted die casting), gravity permanent mold, semi-permanent mold, squeeze, sand mold, spin/centrifugal, or ablation casting. After the casting, the 3 xx casting alloy may be machined and/or tempered. The tempering may include solution heat treating, and then quenching, and then naturally and/or artificially aging. Suitable tempers include the T4, T5, T6, and T7 tempers, for instance. The temper designations used herein are per ANSI H35.1 (2009).
The 3 xx shape cast parts made from the new 3 xx aluminum casting alloys may be used in any suitable application, such as in any of an automotive, aerospace, industrial or commercial transportation application, among others. In one embodiment, the 3 xx shape cast part is an automotive part (e.g., a body-in-white (BIW) part; a suspension part). In one embodiment, the 3 xx shape cast part is included in an automobile. In one embodiment, the 3 xx shape cast part is an aerospace part. In one embodiment, the 3 xx shape cast part is included in an aerospace vehicle. In one embodiment, the 3 xx shape cast part is an industrial part. In one embodiment, the 3 xx shape cast part is a commercial transportation part. In one embodiment, the 3 xx shape cast part is included in a commercial transportation vehicle.
In one embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 265 MPa, when testing in accordance with ASTM E8 and B557. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 270 MPa. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 275 MPa. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 280 MPa. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 285 MPa. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 290 MPa. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 295 MPa. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength of at least 300 MPa, or more. Accompanying these strength embodiments, the new 3 xx shape cast part may also realize an elongation of at least 5%. In one embodiment, the new 3 xx shape cast part should also realize an elongation of at least 6%. In another embodiment, the new 3 xx shape cast part should also realize an elongation of at least 7%. In another embodiment, the new 3 xx shape cast part should also realize an elongation of at least 8%, or more.
In one embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 400, wherein QI=UTS(MPa)+150*log(Elongation). In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 410. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 420. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 430. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 440. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 450. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a Quality Index (QI) of at least 460, or more.
In one embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to realize a tensile yield strength of at least 280 MPa, an elongation of at least 6%, and a Quality Index (QI) of at least 400.
In one embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength that is at least 5% better than the tensile yield strength of a baseline shape cast part, wherein the baseline shape cast part has the same product form, dimensions, geometry, and temper as the new 3 xx shape cast part, but the baseline shape cast part is made from conventional alloy A365, wherein the tensile yield strength is tested in accordance with ASTM E8 and B557. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength that is at least 10% better than the tensile yield strength of a baseline shape cast part made from conventional alloy A365. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength that is at least 15% better than the tensile yield strength of a baseline shape cast part made from conventional alloy A365. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve a tensile yield strength that is at least 20% better than the tensile yield strength of a baseline shape cast part made from conventional alloy A365. In some of the above embodiments, the new 3 xx shape cast part may realize equivalent or better elongation as compared to a baseline shape cast part made from conventional alloy A365.
In one embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve an average staircase fatigue strength that is at least 5% better than the average staircase fatigue strength of a baseline shape cast part, wherein the baseline shape cast part has the same product form, dimensions, geometry, and temper as the new 3 xx shape cast part, but the baseline shape cast part is made from conventional alloy A365, wherein the average staircase fatigue strength is tested in accordance with ASTM E466-15. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve an average staircase fatigue strength that is at least 10% better that the average staircase fatigue strength of a baseline shape cast part made from conventional alloy A365. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve an average staircase fatigue strength that is at least 15% better that the average staircase fatigue strength of a baseline shape cast part made from conventional alloy A365. In another embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (Si, Mg, Cu, Mn, Sr, Ti, Fe, Zn, Al, and impurities) to achieve an average staircase fatigue strength that is at least 20% better that the average staircase fatigue strength of a baseline shape cast part made from conventional alloy A365.
In one embodiment, a new 3 xx shape cast part includes a sufficient amount of the above alloying elements (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 shape cast part (e.g., the same product form, dimensions, geometry, temper) but made from conventional alloy A365, 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.
As used herein, ASTM E8 refers to “ASTM E8/E8M-15a-Standard Test Methods for Tension Testing of Metallic Materials.”
As used herein, ASTM B557 refers to “ASTM B557-15-Standard Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products.”
As used herein, ASTM E466 refers to “ASTM E466-15-Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials.”
As used herein, ASTM G110 refers to “ASTM G110-92(2015)—Standard Practice for Evaluating Intergranular Corrosion Resistance of Heat Treatable Aluminum Alloys by Immersion in Sodium Chloride+Hydrogen Peroxide Solution.”
As used herein, alloy A365 means Aluminum Association alloy 365.0, formerly Silafont-36, defined in Aluminum Association document “Designations and Chemical Composition Limits for Aluminum Alloys in the Form of Castings and Ingot” (2009), having 9.5-11.5 wt. % Si, up to 0.15 wt. % Fe (impurity), up to 0.03 wt. % Cu (impurity), 0.50-0.8 wt. % Mn, 0.10-0.50 wt. % Mg, up to 0.07 wt. % Zn (impurity), 0.04-0.15 wt. % Ti, the balance being aluminum and other impurities (other than Fe, Cu, and Zn), wherein the 365.0 alloy contains not greater than 0.03 wt. % of any one of these other impurities, and wherein the 365.0 alloy contains not greater than 0.10 wt. % in total of these other impurities.
Several 3 xx 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.
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).
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.
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
Several 3 xx 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.
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.
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 3Several 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.
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%.
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, 309 MPa 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.
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.
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.
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.
The fatigue strength results are shown in
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.
Claims
1. A method, comprising:
- (a) shape casting a 3 xx aluminum casting alloy into a shape cast product, wherein the 3 xx aluminum casting alloy comprises: 6.5-11.0 wt. % Si; 0.20-0.80 wt. % Mg; 0.05-0.50 wt. % Cu; 0.10-0.80 wt. % Mn; 0.005-0.050 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 (Al) and impurities, wherein the 3 xx aluminum casting alloy includes not greater than 0.10 wt. % of any one impurity, and wherein the 3 xx aluminum casting alloy includes not greater than 0.35 wt. %, in total, of the impurities, wherein the shape casting step is selected from the group consisting of: high pressure die casting, gravity permanent mold casting, semi-permanent mold casting, squeeze casting, sand mold casting, centrifugal casting, and ablation casting;
- (b) optionally machining the shape cast product;
- (c) tempering the shape cast product, wherein, due to the tempering, the shape cast product is in a T temper.
2. The method of claim 1, wherein the T temper is selected from the group consisting of: T4, T5, T6, and T7 tempers.
3. The method of claim 1, wherein the shape cast product is an automotive product.
Type: Application
Filed: Oct 17, 2022
Publication Date: Mar 2, 2023
Inventors: Xinyan Yan (Murrysville, PA), Jen C. Lin (Export, PA)
Application Number: 17/967,708
