US20190352745A1

US20190352745A1 - Al-Mg-Si-Mn-Fe CASTING ALLOYS

Info

Publication number: US20190352745A1
Application number: US16/405,061
Authority: US
Inventors: Xinyan Yan
Original assignee: Alcoa USA Corp
Current assignee: Alcoa USA Corp
Priority date: 2018-05-07
Filing date: 2019-05-07
Publication date: 2019-11-21
Also published as: KR20200140917A; KR102747986B1; WO2019217319A1; ES2949017T3; EP3589766A1; EP3589766B1; MX2020011679A; PL3589766T3; JP7438134B2; DE202019105466U1; CA3099043A1; EP4234123A3; EP4234123A2; CN110603341A; JP2021523291A; EP3589766A4

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.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application No. 62/667,930, filed May 7, 2018, which is incorporated herein by reference in its entirety.

BACKGROUND

Aluminum alloys are useful in a variety of applications. Aluminum casting (foundry) alloys, for instance, are used in dozen of industries, including, for instance, the automotive and consumer electronics industries.

SUMMARY OF THE INVENTION

Broadly, the present disclosure relates to new aluminum casting (foundry) alloys and associated products. The new aluminum casting alloys generally comprise (and in some instances consist of or consist essentially of) from 2.5 to 5.0 wt. % Mg, from 0.70 to 2.5 wt. % Si, where the weight ratio of magensium to silicon (Mg/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, and 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 realize an improve combination of properties, such as an improved combination of two or more of strength, ductility, castability, die soldering resistance and quality index, among others.
i. Composition
As noted above, the new aluminum casting alloys generally include from 2.5 to 5.0 wt. % Mg. In one embodiment, a new aluminum casting alloy includes not greater than 4.75 wt. % Mg. In another embodiment, a new aluminum casting alloy includes not greater than 4.60 wt. % Mg. In one embodiment, a new aluminum casting alloy includes at least 2.75 wt. % Mg. In another embodiment, a new aluminum casting alloy includes at least 3.0 wt. % Mg.
As noted above, the new aluminum casting alloys generally include from 0.70 to 2.5 wt. % Si. In one embodiment, a new aluminum casting alloy includes at least 0.80 wt. % Si. In another embodiment, a new aluminum casting alloy includes at least 0.90 wt. % Si. In yet another embodiment, a new aluminum casting alloy includes at least 0.95 wt. % Si. In another embodiment, a new aluminum casting alloy includes at least 1.00 wt. % Si. In yet another embodiment, a new aluminum casting alloy includes at least 1.05 wt. % Si. In another embodiment, a new aluminum casting alloy includes at least 1.10 wt. % Si. In yet another embodiment, a new aluminum casting alloy includes at least 1.15 wt. % Si. In another embodiment, a new aluminum casting alloy includes at least 1.20 wt. % Si. In one embodiment, a new aluminum casting alloy includes not greater than 2.4 wt. % Si. In another embodiment, a new aluminum casting alloy includes not greater than 2.3 wt. % Si. In yet another embodiment, a new aluminum casting alloy includes not greater than 2.2 wt. % Si. In another embodiment, a new aluminum casting alloy includes not greater than 2.1 wt. % Si. In yet another embodiment, a new aluminum casting alloy includes not greater than 2.0 wt. % Si.
As noted above, the weight ratio of magnesium to silicon in the new aluminum casting alloys is generally from 1.7:1 to to 3.6:1 (wt. % Mg/wt. % Si). In one embodiment, the weight ratio of magensium to silicon in the new aluminum casting alloy is at least 1.8:1. In another embodiment, the weight ratio of magnesium to silicon in the new aluminum casting alloy is at least 1.85:1. In one embodiment, the weight ratio of magnesium to silicon in the new aluminum casting alloy is not greater than 3.6:1. In another embodiment, the weight ratio of magnesium to silicon in the new aluminum casting alloy is not greater than 3.5:1.
In one embodiment, a new aluminum casting alloy includes an amount of magnesiumn and silicon sufficient to facilitate production of a crack-free cast product (e.g., a crack-free high pressure die cast product). A crack-free product is a product sufficiently free of cracks so that it can be used for its intended purpose. In one embodiment, a new aluminum casting alloy includes an amount of magnesium and silicon sufficient to realize a hot cracking tendency index (HCTI) of not greater than 0.30, such as any of the low HCTI values disclosed herein.
As noted above, the new aluminum casting alloys generally include from 0.40 to 1.5 wt. % Mn. In one embodiment, a new aluminum casting alloy includes at least 0.45 wt. % Mn. In another embodiment, a new aluminum casting alloy includes at least 0.50 wt. % Mn. In yet another embodiment, a new aluminum casting alloy includes at least 0.55 wt. % Mn. In another embodiment, a new aluminum casting alloy includes at least 0.60 wt. % Mn. In one embodiment, a new aluminum casting alloy includes not greater than 1.45 wt. % Mn. In another embodiment, a new aluminum casting alloy includes not greater than 1.40 wt. % Mn. In yet another embodiment, a new aluminum casting alloy includes not greater than 1.35 wt. % Mn. In another embodiment, a new aluminum casting alloy includes not greater than 1.30 wt. % Mn. In yet another embodiment, a new aluminum casting alloy includes not greater than 1.25 wt. % Mn. In another embodiment, a new aluminum casting alloy includes not greater than 1.20 wt. % Mn.
As noted above, the new aluminum casting alloys generally include from 0.10 to 0.60 wt. % Fe. In one embodiment, a new aluminum casting alloy includes at least 0.12 wt. % Fe. In another embodiment, a new aluminum casting alloy includes at least 0.15 wt. % Fe. In yet another embodiment, a new aluminum casting alloy includes at least 0.20 wt. % Fe. In another embodiment, a new aluminum casting alloy includes at least 0.25 wt. % Fe. In yet another embodiment, a new aluminum casting alloy includes at least 0.30 wt. % Fe. In another embodiment, a new aluminum casting alloy includes at least 0.35 wt. % Fe. In one embodiment, a new aluminum casting alloy includes not greater than 0.55 wt. % Fe. In another embodiment, a new aluminum casting alloy includes not greater than 0.50 wt. % Fe. In yet another embodiment, a new aluminum casting alloy includes not greater than 0.45 wt. % Fe.
In one embodiment, a new aluminum casting alloy includes an amount of iron and manganse sufficient to facilitate formation of alpha phase particles while restricting formation of beta phase particles. In one embodiment, at least due to the iron content, a new aluminum casting alloy includes not greater than 0.012 wt. % of β-Al5FeSi compounds. In another embodiment, a new aluminum casting alloy includes not greater than 0.010 wt. % of β-Al5FeSi compounds. In yet another embodiment, a new aluminum casting alloy includes not greater than 0.008 wt. % of β-Al5FeSi compounds. In another embodiment, a new aluminum casting alloy includes not greater than 0.006 wt. % of β-Al5FeSi compounds. In yet another embodiment, a new aluminum casting alloy includes not greater than 0.004 wt. % of β-Al5FeSi compounds. In another embodiment, a new aluminum casting alloy includes not greater than 0.002 wt. % of β-Al5FeSi compounds. In yet another embodiment, a new aluminum casting alloy includes not greater than 0.001 wt. % of β-Al5FeSi compounds. In another embodiment, a new aluminum casting alloy includes not greater than 0.0005 wt. % of β-Al5FeSi compounds.
In one embodiment, a new aluminum casting alloy may include an amount of magnesium and silicon sufficient to satisfy the following requirement: (0.4567*Mg−0.5)<=Si <=(0.4567*Mg +0.2).
In one embodiment, a new aluminum casting alloy may include an amount of magnesium, silicon, manganese and iron sufficient to satisfy the following requirements:
(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).
As noted above, the new aluminum casting alloys may optionally include up to 0.15 wt. % Ti. In one embodiment, a new aluminum casting alloy includes at least 0.01 wt. % Ti. In another embodiment, a new aluminum casting alloy includes at least 0.03 wt. % Ti. In yet another embodiment, a new aluminum casting alloy includes at least 0.05 wt. % Ti. In another embodiment, a new aluminum casting alloy includes at least 0.07 wt. % Ti. In one embodiment, a new aluminum casting alloy includes not greater than 0.13 wt. % Ti. In another embodiment, a new aluminum casting alloy includes not greater than 0.115 wt. % Ti. In another embodiment, a new aluminum casting alloy includes not greater than 0.10 wt. % Ti. In one embodiment, a new aluminum casting alloy include an amount of titanium sufficient to faciltiate grain refining while resticting/avoiding formation of primary titanium-containing particles. In some embodiments, titanium is included in a new aluminum casting alloy as an impurity.
As noted above, the new aluminum casting alloys may optionally include up to 0.10 wt. % Sr. In one embodiment, a new aluminum casting alloy includes an amount of strontium sufficient to faciltiate modification of the Mg₂Si eutectic while resticting/avoiding formation of primary strontium-containing particles. In one embodiment, a new aluminum casting alloy includes at least 0.005 wt. % Sr. In one embodiment, a new aluminum casting alloy includes not greater than 0.08 wt. % Sr. In another embodiment, a new aluminum casting alloy includes not greater than 0.05 wt. % Sr. In some embodiments, strontium is included in a new aluminum casting alloy as an impurity.
As noted above, the new aluminum casting alloys may optionally include up to 0.15 wt. % of any of Zr, Sc, Hf, V, and Cr. In one embodiment, a new aluminum casting alloy includes an amount of zirconiun, scandium, hafnium, vanadium, and/or chromium sufficient to facilitate solid solution strengthening while restricting/avoiding formation of primary particles containing zirconium, scandium, hafnium, vanadium, and chromium. In one embodiment, a new aluminum casting alloy includes at least 0.01 wt. % of any of Zr, Sc, Hf, V, and Cr. In another embodiment, a new aluminum casting alloy includes at least 0.03 wt. % of any of Zr, Sc, Hf, V, and Cr. In yet another embodiment, a new aluminum casting alloy includes at least 0.05 wt. % of any of Zr, Sc, Hf, V, and Cr. In one embodiment, a new aluminum casting alloy includes not greater than 0.10 wt. % of any of Zr, Sc, Hf, V, and Cr. In some embodiments, zirconium is included in a new aluminum casting alloy as an impurity. In some embodiments, scandium is included in a new aluminum casting alloy as an impurity. In some embodiments, hafnium is included in a new aluminum casting alloy as an impurity. In some embodiments, vanadium is included in a new aluminum casting alloy as an impurity. In some embodiments, chromium is included in a new aluminum casting alloy as an impurity.
The balance of the new aluminum casting alloys is generally aluminum and unavoidable impurities. In one embodiment, a new aluminum casting alloy comprises not greater than 0.30 wt. % of the unavoiable impurities, and wherein the new aluminum casting alloy comprises not greater than 0.10 wt. % of any one element of the unavoiable impurities. In another embodiment, a new aluminum casting alloy comprises not greater than 0.15 wt. % of the unavoiable impurities, and wherein the new aluminum casting alloy comprises not greater than 0.05 wt. % of any one element of the unavoidable impurities. In yet another embodiment, a new aluminum casting alloy comprises not greater than 0.10 wt. % of the unavoiable impurities, and wherein the new aluminum casting alloy comprises not greater than 0.03 wt. % of any one element of the unavoiable impurities.
ii. Processing
The new aluminum casting alloys may be cast using any suitable casting method. In one embodiment, a new aluminum casting alloy is a direct chill cast as an ingot or billet. In another embodiment, a new aluminum casting alloy is shape cast into a shape cast product (e.g., a complex shape cast product, such as a complex automotive component). In one embodiment, the shape cast product is an automotive structural component. In another embodiment, the shape cast product is a door frame. In another embodiment, the shape cast product is a shock tower. In another embodiment, the shape cast product is a tunnel structure for an automobile.
In one embodiment, the shape casting comproses high pressure die casting. In another embodiment, the shape casting comprises permanent mold casting.
The new aluminum casting alloys do not require a solution heat treatment step. The new aluminum casting alloys may be provided, therefore, in the appropriate temper, such as in the F temper or the T5 temper.
iii. Properties
As noted above, the new aluminum casting alloys may realize an improved combination of properties, such as an improved combination of at least two of strength, ductility, castability, die soldering resistance and quality index. Mechanical properties may be measured in accordance with ASTM E8 and B557 (e.g., when directionally solidified). Castability may be measured using the HCTI method described herein. Die soldering resistance may be determined by casting the alloy.
In one embodiment, a new aluminum casting alloy realizes an ultimate tensile strength of at least 200 MPa. In another embodiment, a new aluminum casting alloy realizes an ultimate tensile strength of at least 210 MPa. In yet another embodiment, a new aluminum casting alloy realizes an ultimate tensile strength of at least 220 MPa. In another embodiment, a new aluminum casting alloy realizes an ultimate tensile strength of at least 230 MPa.
In one embodiment, a new aluminum casting alloy realizes a tensile yield strength of at least 100 MPa. In another embodiment, a new aluminum casting alloy realizes an tensile yield strength of at least 105 MPa. In yet another embodiment, a new aluminum casting alloy realizes an tensile yield strength of at least 110 MPa. In another embodiment, a new aluminum casting alloy realizes an tensile yield strength of at least 115 MPa. In another embodiment, a new aluminum casting alloy realizes an tensile yield strength of at least 120 MPa. In another embodiment, a new aluminum casting alloy realizes an tensile yield strength of at least 125 MPa. Any of the above tensile yield strength values may be realized with any of the above ultimate tensile strength values.
In one embodiment, a new aluminum casting alloy realizes an elongation of at least 7%. In another embodiment, a new aluminum casting alloy realizes an elongation of at least 8%. In yet another embodiment, a new aluminum casting alloy realizes an elongation of at least 9%. In another embodiment, a new aluminum casting alloy realizes an elongation of at least 10%. In yet another embodiment, a new aluminum casting alloy realizes an elongation of at least 11%. In another embodiment, a new aluminum casting alloy realizes an elongation of at least 12%. In yet another embodiment, a new aluminum casting alloy realizes an elongation of at least 13%. In another embodiment, a new aluminum casting alloy realizes an elongation of at least 14%. In yet another embodiment, a new aluminum casting alloy realizes an elongation of at least 15%. In another embodiment, a new aluminum casting alloy realizes an elongation of at least 16%, or higher. Any of the above elongation values may be realized with any of the above ultimate tensile strength or tensile yield strength values.
In one embodiment, a new aluminum casting alloy realizes a HCTI of not greater than 0.30. In another embodiment, a new aluminum casting alloy realizes a HCTI of not greater than 0.25. In yet another embodiment, a new aluminum casting alloy realizes a HCTI of not greater than 0.20. In another embodiment, a new aluminum casting alloy realizes a HCTI of not greater than 0.15, or lower.
In one embodiment, a new aluminum casting alloy is die soldering resistant wherein the as-cast aluminum alloy product is removed from the die without damage to the cast product and/or without sticking to the die. Die soldering can occur during high pressure die casting wherein molten aluminum solders to the die surface. In some embodiments, the new aluminum casting alloys described herein may be cast without being soldered to the die.
These and other combination of features are disclosed in the below Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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.

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.

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.

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

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

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

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

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.

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.

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.

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

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

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.

The hot cracking tendency index (HCTI) of an alloy is defined as
$HCTI = \frac{\sum diameter of the cracked rod}{(4 + 6 + 8 + 10 + 12 + 14 + 16)}$
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 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

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 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.

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

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 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.

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

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 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

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 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.

These results are unexpected. The mechanical properties of Al—Si 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 (ICME—Integrated Computational Materials Engineering). These results show that, by controlling Fe and Mn contents, formation of unwanted needle-shaped β-Al₅FeSi can be potentially avoided. FIGS. 5 a, 5 b and 6 show the correlation between manganese and iron content and the volume fraction on β-Al₅FeSi and α-Al₁₅FeMn₃Si₂phase particles (for a Al -3.6Mg-1.5Si alloys). Adding Mn to the Al—Mg—Si alloys can promote formation of α-Al₁₅FeMn₃Si₂phase and restrict or prevent formation of β-Al₅FeSi 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 β-Al₅FeSi phase. As shown in FIG. 6, the amount of β-Al₅FeSi 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 β-Al₅FeSi phase within the alloy.

EXAMPLE 6

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 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.

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 -7 d.

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

Based on the prior experiments, various aluminum alloy compositions were modeled. The results are shown in FIGS. 8a -8 b. These modeling results indicate that for an Al—Mg—Si 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*Mg−0.5)<=Si<=(0.4567*Mg+0.2)
Similar modeling was done on additional aluminum alloys, as shown in FIGS. 8c -8 d. 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:
(0.4567*Mg+0.2*Mn+0.25*Fe−0.6)<=Si<=(0.4567*Mg+0.2*Mn+0.25*Fe)
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.

Claims

What is claimed is:

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*Mg−0.5)<=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 β-Al₅FeSi 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;

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.