US20190390305A1

US20190390305A1 - Semi-solid die-casting aluminum alloy and method for preparing semi-solid die-casting aluminum alloy casting

Info

Publication number: US20190390305A1
Application number: US16/465,321
Authority: US
Inventors: Yongxi Jian; Chunmeng ZHANG; Qiang Guo
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2016-12-02
Filing date: 2017-11-16
Publication date: 2019-12-26
Also published as: EP3550046A4; CN108149083A; EP3550046A1; CN108149083B; WO2018099272A1

Abstract

The present disclosure provides a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting. The semi-solid die-casting aluminum alloy contains alloying elements, inevitable impurities and the balance of aluminum element. Based on the total weight of the semi-solid die-casting aluminum alloy, the alloying elements include: 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % of Ti and 0.01 to 0.35 wt % of rare earth element.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Chinese Patent Application No. CN 201611096735.4 filed in China on Dec. 2, 2016, the entire content of which is hereby incorporated by reference.

TECHNOLOGY FIELD

The present disclosure relates to the field of alloys and, in particular, to a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting.

BACKGROUND

Die casting is a liquid molding method. Due to the high injection speed, the liquid easily forms turbulent flow in the mold cavity, and the air in the mold cavity is drawn into the product. When the liquid hits the mold, the temperature difference is large, the liquid on the surface is rapidly solidified, which increases the flow resistance of the core liquid, so it cannot be well fused to form a cold partition. Due to the introduction of oxides or some other impurities in the alloy smelting and casting process, the product performance is ultimately lowered.
With the rapid development of 3C (Computer, communication, and consumer electronics) and automotive products, die-casting aluminum alloys have been rapidly applied. By the 1980s, 68% of aluminum alloy components in the United States were produced by die-casting technology. At present, the die-casting aluminum alloys used in the industry mainly include aluminum-silicon alloys, aluminum-magnesium alloys, aluminum-zinc alloys, aluminum-silicon-copper alloys, and aluminum-silicon-magnesium alloys.
The most commonly used die-casting alloy for die casting is ADC12, which has a yield strength of about 190 MPa, a tensile strength of about 280 MPa, and an elongation of 2 to 3%, and cannot be strengthened by heat treatment. The wrought aluminum alloy (including aluminum alloy for extrusion, forging, rolling, etc.) has high mechanical properties and stable performance, but due to the harsh process conditions and high equipment requirements, it is impossible to form complicated parts, and it is impossible to realize the demands of simplification and integration for automobile parts.

SUMMARY

An objective of the present disclosure is to provide a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting. The semi-solid die-casting aluminum alloy has high strength and high plasticity, can be subjected to high pressure casting, and can form various complicated parts and ensure high mechanical properties.
To achieve the above objective, the present disclosure provides a semi-solid die-casting aluminum alloy, containing alloying elements, inevitable impurities and the balance of an aluminum element; based on the total weight of the semi-solid die-casting aluminum alloy, the alloying elements include: 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % of Ti and 0.01 to 0.35 wt % of rare earth element.
Optionally, based on the total weight of the semi-solid die-casting aluminum alloy, the alloying elements include: 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % of Ti and 0.15 to 0.25 wt % of rare earth element.
Optionally, the rare earth element includes at least one of La, Ce, Pr and Nd.
Optionally, the impurities in the semi-solid die-casting aluminum alloy are not more than 0.8 wt %.
Optionally, the ratio of the weight content of Ti to Cu is 1:(14 to 90).
Optionally, the semi-solid die-casting aluminum alloy includes 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % Ti, 0.01 to 0.35 wt % of rare earth element, no more than 0.8 wt % of impurities and the balance of aluminum.
Optionally, the semi-solid die-casting aluminum alloy includes 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % Ti, 0.15 to 0.25 wt % of rare earth element, no more than 0.7 wt % of impurities and the balance of aluminum.
Optionally, the semi-solid die-casting aluminum alloy has a tensile strength of not less than 370 MPa, a yield strength of not less than 290 MPa, and an elongation of not less than 5.5%.
Optionally, the semi-solid die-casting aluminum alloy has a tensile strength of not less than 380 MPa, a yield strength of not less than 300 MPa, and an elongation of not less than 6%.
The present disclosure further provides a method for preparing a semi-solid die-casting aluminum alloy casting, including: after performing ratio smelting on aluminum alloy raw materials, performing semi-solid die casting to obtain the semi-solid die-casting aluminum alloy casting; where the aluminum alloy raw materials are such that the obtained semi-solid die-casting aluminum alloy casting includes: based on the total weight of the semi-solid die-casting aluminum alloy casting, 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % of Ti, 0.01 to 0.35 wt % of rare earth element, and the balance of aluminum and inevitable impurities.
Optionally, the aluminum alloy raw materials are such that the obtained semi-solid die-casting aluminum alloy casting includes: based on the total weight of the semi-solid die-casting aluminum alloy casting, 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % of Ti, 0.15 to 0.25 wt % of rare earth element, and the balance of aluminum and inevitable impurities.
Optionally, the aluminum alloy raw materials are elemental metals or metal alloys.
Optionally, the aluminum alloy raw materials are elemental aluminum or an alloy of aluminum, elemental silicon or an alloy of silicon, elemental copper or an alloy of copper, elemental manganese or an alloy of manganese, elemental titanium or an alloy of titanium, and an elemental rare earth element or an alloy containing a rare earth element.
Optionally, the aluminum alloy raw materials are elemental aluminum, an Al—Si alloy, an Al—Ti alloy, an Al—Cu alloy, an Al—Mn alloy and an Al—Re intermediate alloy.
Optionally, the purity of the elemental metal is 99.9 wt % or more, and the total content of the alloying elements in the metal alloy is 99.9 wt % or more.
Through the above technical solutions, according to the semi-solid die-casting aluminum alloy of the present disclosure, the adjustment and optimization of the formula and the addition of rare earth elements have the purification effect of removing gases and impurities and the modification effect of refining crystal grains on the alloy melt, and also increase the melt fluidity and enhance the casting properties. The method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure adopts the above semi-solid die-casting aluminum alloy for semi-solid die casting. The method can form various complicated components, enhances the mechanical properties of the casting, reduces the defects of the casting, and enhances the yield.
Other features and advantages of the present disclosure will be described in detail in the detailed description which follows.

DETAILED DESCRIPTION

Specific implementations of the present disclosure are described in detail below. It should be understood that the specific implementations described herein are merely illustrative of the present disclosure and are not intended to limit the present disclosure.
The present disclosure provides a semi-solid die-casting aluminum alloy, containing alloying elements, inevitable impurities and the balance of an aluminum element; based on the total weight of the semi-solid die-casting aluminum alloy, the alloying elements include: 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % of Ti and 0.01 to 0.35 wt % of rare earth element.
According to the semi-solid die-casting aluminum alloy of the present disclosure, the adjustment and optimization of the formula and the addition of rare earth elements have the purification effect of removing gases and impurities and the modification effect of refining crystal grains on the alloy melt, and also increase the melt fluidity and enhance the casting properties. According to the semi-solid die-casting aluminum alloy of the present disclosure, when the composition of the semi-solid die-casting aluminum alloy is within the above range, high mechanical properties can be obtained while good casting properties are obtained. The semi-solid die-casting aluminum alloy obtained by using the formula has a tensile strength of not less than 370 MPa, a yield strength of not less than 290 MPa, and an elongation of not less than 5.5%.
According to the present disclosure, to further enhance the mechanical properties and casting properties of the semi-solid die-casting aluminum alloy, optionally, based on the total weight of the semi-solid die-casting aluminum alloy, the alloying elements include: 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % of Ti and 0.15 to 0.25 wt % of rare earth element. The semi-solid die-casting aluminum alloy obtained according to the formula has a tensile strength of not less than 380 MPa, a yield strength of not less than 300 MPa, and an elongation of not less than 6%.
According to the present disclosure, the kind of the rare earth element is not particularly limited, may be a conventional kind well known to those skilled in the art, and may be a single kind of rare earth element or mixed rare earths. To reduce the raw material cost, optionally, the rare earth element may include at least one of La, Ce, Pr and Nd, and the relative content of each rare earth element is also not particularly required. The above rare earth element may be a commercially available product and is industrial mixed rare earths.
According to the present disclosure, the purity of the semi-solid die-casting aluminum alloy is one of the important factors affecting the performance of the aluminum alloy. To make the semi-solid die-casting aluminum alloy of the present disclosure excellent in performance, optionally, the impurities in the semi-solid die-casting aluminum alloy are not more than 0.8 wt %.
According to the present disclosure, the addition of the metal element titanium in the semi-solid die-casting aluminum alloy can refine the crystal grains, enhance the strength and plasticity of the alloy, improve the fluidity of the alloy and enhance the casting properties. At the same time, the added metal element copper can form a Ti₂Cu₃phase with titanium and be distributed at the grain boundary, so that the grain boundary slip during alloy stretching is effectively suppressed, thereby enhancing the strength of the alloy. To further enhance of the effect of enhancing the performance of the semi-solid die-casting aluminum alloy by the above two elements, optionally, the ratio of the weight content of Ti to Cu may be 1:(7 to 350), preferably 1:(14 to 90).
To further enhance the mechanical properties and casting properties of the semi-solid die-casting aluminum alloy, optionally, the semi-solid die-casting aluminum alloy may include 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % Ti, 0.01 to 0.35 wt % of rare earth element, no more than 0.8 wt % of impurities and the balance of aluminum.
Optionally, the semi-solid die-casting aluminum alloy may include 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % Ti, 0.15 to 0.25 wt % of rare earth element, no more than 0.7 wt % of impurities and the balance of aluminum.
The present disclosure further provides a method for preparing a semi-solid die-casting aluminum alloy casting, including: after performing ratio smelting on aluminum alloy raw materials, performing semi-solid die casting to obtain the semi-solid die-casting aluminum alloy casting, where the aluminum alloy raw materials are such that the obtained semi-solid die-casting aluminum alloy casting includes: based on the total weight of the aluminum alloy casting, 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % of Ti, 0.01 to 0.35 wt % of rare earth element, and the balance of aluminum and inevitable impurities.
According to the method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure, to obtain a semi-solid die-casting aluminum alloy casting having higher mechanical properties, in an optional case, the aluminum alloy raw materials are such that the obtained semi-solid die-casting aluminum alloy casting includes: based on the total weight of the semi-solid die-casting aluminum alloy casting, 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % of Ti, 0.15 to 0.25 wt % of rare earth element, and the balance of aluminum and inevitable impurities.
According to the method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure, the melting may be performed in a smelting furnace, and the aluminum alloy raw materials added to the smelting furnace may be simple substances or metal alloys, as long as the composition of the aluminum alloy obtained by smelting the added aluminum alloy raw materials is within the above range. In an optional case, the aluminum alloy raw materials may be elemental aluminum or an alloy of aluminum, elemental silicon or an alloy of silicon, elemental copper or an alloy of copper, elemental manganese or an alloy of manganese, elemental titanium or an alloy of titanium, and an elemental rare earth element or an alloy containing a rare earth. In an optional case, the above aluminum alloy raw materials are elemental aluminum, an Al—Si alloy, an Al—Ti alloy, an Al—Cu alloy, an Al—Mn alloy and an Al—Re intermediate alloy. Further, to prevent the introduction of impurities from affecting the performance of the aluminum alloy, the purity of the elemental metal is 99.9 wt % or more, and the total content of the alloying elements in the alloy is 99.9 wt % or more.
According to the method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure, the semi-solid die-casting aluminum alloy casting is obtained by performing semi-solid die casting after performing ratio smelting on the aluminum alloy raw materials. The smelting and semi-solid die casting can employ conventional methods and operating conditions, and the present disclosure does not impose any particular requirements.
For example, the smelting process may adopt the existing steps of material preparation→melting→refining→slag removing→casting. Specifically, the method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure may include the following steps:
Step 1: Material preparation: 1) raw materials: a pure aluminum ingot (purity≥99.9 wt %), an Al—Si intermediate alloy, an Al—Ti intermediate alloy, an Al—Cu intermediate alloy, an Al—Mn intermediate alloy and an Al—Re intermediate alloy; and 2) fluxes: a covering agent, a refining agent and a modifier, which may be the existing covering agent, refining agent and modifier for aluminum alloy preparation, for example, the covering agent SY-LF1, the refining agent hexachloroethane and the modifier K2ZrF6.
Step 2: Drying: the prepared raw materials are dried, where the pure aluminum ingot is dried at a temperature of 100° C.±10° C., the Al—Si intermediate alloy, the Al—Ti intermediate alloy, the Al—Cu intermediate alloy, the Al—Mn intermediate alloy and the Al—Re intermediate alloy are dried at a temperature of 150° C.±10° C., and the purpose of drying is to remove moisture from the raw materials.
Step 3: Melt alloying: the inner wall of a crucible is coated with the prepared covering agent, the crucible is preheated to 200 to 250° C., the weighed aluminum ingot, Al—Si intermediate alloy, Al—Ti intermediate alloy, Al—Cu intermediate alloy, Al—Mn intermediate alloy and Al—Re intermediate alloy ingot are placed into the crucible, and heated and melted after the addition of the covering agent, and the alloys are stirred uniformly after fully melted, where the time of the entire melting process is controlled within 2 to 3 h, and the final temperature of the aluminum alloy melt is controlled at 750 to 770° C.
Step 4: Refining: the purpose of refining is to remove non-metallic inclusions in the alloy liquid; at 700 to 720° C., a bell jar is used to press the refining agent hexachloroethane into about ⅔ below the surface of the melt in batches, and is rotated clockwise uniformly and slowly, and when the hexachloroethane is fully reacted, the inclusions and gases in the melt are taken out. The speed of stirring is low. The amount of hexachloroethane is related to the alloy composition and the mass of the original ingot, and is generally 0.5 wt % to 0.7 wt % of the charge. Melting is performed in a resistance furnace, and the refining time is within 10 min.
Step 5: Slag removing: after fully refining with the hexachloroethane, the bell jar is taken out, the residual oxides are removed, and the inclusions on the surface of the melt are removed with a slag spoon.
Step 6: Casting: after the alloy slag is removed, pouring should be immediately performed after 4 to 10 min of heat preservation to obtain an alloy ingot for die casting or a die-cast block. The pouring temperature is generally required to be 720 to 750° C.
Step 7: Die Casting: the above-mentioned alloy ingot for die casting or die-cast block is die-cast into a sample by a conventional semi-solid die casting process, thereby obtaining the aluminum alloy casting of the present disclosure.
The aluminum alloy and a method for preparing the same of the present disclosure are further described below by way of embodiments. However, the present disclosure is not limited to the embodiments listed below.
In the following embodiments and comparative examples of the present disclosure, the rare earth element is mixed rare earths (containing 39.8 wt % of La and 58.8 wt % of Ce).

Embodiment 1

This embodiment is for explaining a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure.
The semi-solid die-casting aluminum alloy included: based on the total weight of the semi-solid die-casting aluminum alloy, 8.5 wt % of Si, 4.0 wt % of Cu, 0.55 wt % of Mn, 0.15 wt % of Ti, 0.20 wt % of rare earth element, and the balance of aluminum.
The aluminum ingot, the Al—Si intermediate alloy, the Al—Ti intermediate alloy, the Al—Cu intermediate alloy, the Al—Mn intermediate alloy and the Al—Re intermediate alloy ingot measured according to the above semi-solid die-casting aluminum alloy composition were placed into a crucible coated with a covering agent and preheated to 220° C., and were heated and melted after the addition of the covering agent, and the alloys were stirred uniformly after fully melted, where the melting process was 2.5 h, and the final temperature of the aluminum alloy melt was 750° C.; at 700 to 720° C., a bell jar was used to press the refining agent hexachloroethane into about ⅔ below the surface of the melt in batches, and was rotated clockwise uniformly and slowly, for refining for 8 min where the amount of hexachloroethane was 0.5 wt % of the charge; after fully refining, the bell jar was taken out, the residual oxides were removed, and the inclusions on the surface of the melt were removed with a slag spoon; after 5 min of heat preservation, pouring was performed to obtain an aluminum alloy ingot Z1, where the pouring temperature was 750° C.; and the above aluminum alloy ingot Z1 was die-cast into a sample by a conventional semi-solid die casting process, thereby obtaining the aluminum alloy casting Al of this embodiment.

Embodiment 2

This embodiment is for explaining a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure.
The method of Embodiment 1 was employed, except that the semi-solid die-casting aluminum alloy included: based on the total weight of the semi-solid die-casting aluminum alloy, 9.5 wt % of Si, 3.5 wt % of Cu, 0.5 wt % of Mn, 0.01 wt % of Ti, 0.01 wt % of rare earth element and the balance of aluminum, thereby obtaining the aluminum alloy casting A2 of this embodiment.

Embodiment 3

This embodiment is for explaining a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure.
The method of Embodiment 1 was employed, except that the semi-solid die-casting aluminum alloy included: based on the total weight of the semi-solid die-casting aluminum alloy, 7.5 wt % of Si, 4.8 wt % of Cu, 0.75 wt % of Mn, 0.5 wt % of Ti, 0.35 wt % of rare earth element and the balance of aluminum, thereby obtaining the aluminum alloy casting A3 of this embodiment.

Embodiment 4

This embodiment is for explaining a semi-solid die-casting aluminum alloy and a method for preparing a semi-solid die-casting aluminum alloy casting of the present disclosure.
The method of Embodiment 1 was employed, except that the semi-solid die-casting aluminum alloy included: based on the total weight of the semi-solid die-casting aluminum alloy, 9.0 wt % of Si, 4.4 wt % of Cu, 0.52 wt % of Mn, 0.10 wt % of Ti, 0.15 wt % of rare earth element and the balance of aluminum, thereby obtaining the aluminum alloy casting A4 of this embodiment.

Comparative Example 1

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The method and the raw materials of Embodiment 1 were employed except that no rare earth element was added, thereby obtaining the aluminum alloy casting B1 of this comparative example.

Comparative Example 2

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The method and the raw materials of Embodiment 1 were employed except that the content of the rare earth element in the semi-solid die-casting aluminum alloy was 0.5 wt %, thereby obtaining the aluminum alloy casting B2 of this comparative example.

Comparative Example 3

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing the aluminum alloy casting different from the present disclosure.
The method and the raw materials of Embodiment 1 were employed except that the content of the Si in the semi-solid die-casting aluminum alloy was 10 wt %, thereby obtaining the aluminum alloy casting B3 of this comparative example.

Comparative Example 4

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The method and the raw materials of Embodiment 1 were employed except that the content of the Si in the semi-solid die-casting aluminum alloy was 7 wt %, thereby obtaining the aluminum alloy casting B4 of this comparative example.

Comparative Example 5

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing the aluminum alloy casting different from the present disclosure.
The method and the raw materials of Embodiment 1 were employed except that the content of the Cu in the semi-solid die-casting aluminum alloy was 5 wt %, thereby obtaining the aluminum alloy casting B5 of this comparative example.

Comparative Example 6

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The method and the raw materials of Embodiment 1 were employed except that the content of the Cu in the semi-solid die-casting aluminum alloy was 3 wt %, thereby obtaining the aluminum alloy casting B6 of this comparative example.

Comparative Example 7

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The method of Embodiment 1 was employed except that a commercially available ADC12 aluminum alloy ingot was used as the ingot, thereby obtaining the aluminum alloy sample B7.

Comparative Example 8

This comparative example is for explaining a semi-solid die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The method of Embodiment 1 was employed except that a commercially available A356.2 aluminum alloy ingot was used as the ingot, thereby obtaining the aluminum alloy sample B8.

Comparative Example 9

This comparative example is for explaining a die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
The raw materials of Embodiment 1 were employed except that a conventional die casting method was used, thereby obtaining the aluminum alloy sample B9.

Comparative Example 10

This comparative example is for explaining a die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
Pure aluminum (A00 aluminum), an aluminum-manganese alloy (AlMn10), an aluminum-silicon alloy (AlSi12), an aluminum-iron alloy (AlFe10), an aluminum-copper alloy (Al-50Cu), pure magnesium (99.9), pure zinc (99.95), an aluminum-titanium-carbon-boron alloy, magnesium-lanthanum-cerium (Mg—LaCe) and magnesium-yttrium (Mg—Y) were subjected to mixture calculation, smelting and pouring. The contents of the main elements of the finally obtained alloy were as follows: Si: 6.0 wt %, Cu: 0.5 wt %, Fe: 0.42 wt %, Mn: 0.05 wt %, Mg: 1.0 wt %, Zn: 1.5 wt %, Ti: 0.05 wt %, C: 0.002 wt %, LaCe: 0.20 wt %, Y: 0.12 wt %, and the balance of Al and inevitable impurities. A conventional die casting method was employed to obtain the aluminum alloy sample B10.

Comparative Example 11

This comparative example is for explaining a die-casting aluminum alloy and a method for preparing an aluminum alloy casting different from the present disclosure.
(1) A pure magnesium ingot and intermediate alloys Al—Si, Al—Mn, Al—Cu, Al—Ti were preheated to 180 to 240° C., the temperature was kept within the range of 740 to 760° C. after pure aluminum was melted, the pure magnesium ingot and the intermediate alloys Al—Si, Al—Mn, Al—Cu, Al—Ti were sequentially added into the aluminum liquid, and after being melted, they were kept at 740° C. for 30 minutes to be sufficiently homogenized, where the weight percents of the ingredients in the above materials were Si: 8.5 to 11.5%, Mn: 0.1 to 0.8%, Cu: 0.5 to 3.0%, Mg: 0.25 to 0.5%, Ti: 0.15 to 0.35%, and other impurities≤0.4% (where Fe<0.8%, P<0.004%).
(2) The temperature of the alloy liquid was raised to 780° C., the mixed rare earths were added, the surface scum was removed after the mixed rare earths were melted, the mixture was stirred for 3 to 6 minutes to homogenize the composition, and after stirring, the temperature of the alloy liquid was raised to 770 to 780° C., and then kept to stand for 30 minutes, where the total weight of the mixed rare earths is not more than 1%, and each of La, Ce, Sm and Nd is less than 0.35% by weight.
(3) After the alloy liquid was cooled to 750° C. and refined for 15 minutes, the alloy liquid was cooled to 710° C. and subjected to slag removal, then the alloy liquid was cooled to 690° C. and subjected to gas removal, finally the alloy liquid after slag removal and gas removal was cooled to at 680° C. and subjected to die casting, and the heat treatment process was performed after the casting was formed. The casting was subjected to solution treatment at a temperature of higher than 545° C. for 3 hours, and then subjected to aging treatment at a temperature of 165° C. for 6 to 12 hours, thereby obtaining the aluminum alloy sample B11.
Test
This test was used to determine the mechanical properties of the semi-solid die-casting aluminum alloy castings obtained in Embodiments 1 to 4 and Comparative Examples 1 to 11 at room temperature.
For the tensile strength, yield strength and elongation of the aluminum alloy castings tested with reference to “GB/T 228.1-2010 Metallic Materials-Tensile Testing-Part 1: Method of test at room temperature”, the specific results are shown in Table 1.

TABLE 1

	Yield Strength	Breaking Strength	Elongation
Embodiment	(MPa)	(MPa)	(%)

Embodiment 1	310	392	8.5
Embodiment 2	300	371	7.0
Embodiment 3	291	376	5.5
Embodiment 4	305	385	8.0
Comparative example 1	254	332	5.5
Comparative example 2	296	367	7.0
Comparative example 3	280	371	6.0
Comparative example 4	261	323	5.0
Comparative example 5	290	342	4.0
Comparative example 6	243	296	5.0
Comparative example 7	185	292	2.5
Comparative example 8	251	310	8.0
Comparative example 9	174	278	2
Comparative example 10	200	300	6.2
Comparative example 11	230	308	5.0

It can be seen from the comparison of the results of Embodiments 1 to 4 and Comparative Examples 1 to 11 that the semi-solid die-casting aluminum alloy of the present disclosure has good mechanical properties and casting properties, and the semi-solid die-casting aluminum alloy has a tensile strength of not less than 370 MPa, a yield strength of not less than 290 MPa, and an elongation of not less than 5.5%. In particular, the optional alloying elements in the present disclosure include: 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % of Ti and 0.15 to 0.25 wt % of rare earth element, the semi-solid die-casting aluminum alloy obtained according to the formula has a tensile strength of not less than 380 MPa, a yield strength of not less than 300 MPa, and an elongation of not less than 6%. It can be seen from the comparison of the data of Embodiment 1 and Embodiment 4 with Embodiments 2 to 3 that in the case where the ratio of the weight content of Ti to Cu of the present disclosure is 1:(14 to 90), the semi-solid die-casting aluminum alloy of the present disclosure has better mechanical properties and casting properties.
Although optional implementations of the present disclosure are described in detail above, the present disclosure is not limited to specific details in the foregoing implementations. Various variations can be made to the technical solutions of the present disclosure within the scope of the technical idea of the present disclosure, and such variations all fall within the protection scope of the present disclosure.
It should be further noted that the specific technical features described in the foregoing specific implementations can be combined in any appropriate manner provided that no conflict occurs. To avoid unnecessary repetition, various possible combination manners are not further described in the present disclosure.
In addition, various different implementations of the present disclosure may alternatively be combined randomly. Such combinations should also be considered as the content disclosed in the present disclosure provided that these combinations do not depart from the concept of the present disclosure.

Claims

1. A semi-solid die-casting aluminum alloy, comprising:

alloying elements, inevitable impurities, and a balance of aluminum element,

wherein based on a total weight of the semi-solid die-casting aluminum alloy, the alloying elements comprise:

7.5 to 9.5 wt % of Si,

3.5 to 4.8 wt % of Cu,

0.5 to 0.75 wt % of Mn,

0.01 to 0.5 wt % of Ti, and

0.01 to 0.35 wt % of rare earth element.

2. The semi-solid die-casting aluminum alloy according to claim 1, wherein based on the total weight of the semi-solid die-casting aluminum alloy, the alloying elements comprise:

8.0 to 9.0 wt % of Si,

3.5 to 4.5 wt % of Cu,

0.5 to 0.6 wt % of Mn,

0.05 to 0.25 wt % of Ti, and

0.15 to 0.25 wt % of rare earth element.

3. The semi-solid die-casting aluminum alloy according to claim 1, wherein the rare earth element comprises at least one of La, Ce, Pr and Nd.

4. The semi-solid die-casting aluminum alloy according to claim 1, wherein the impurities in the semi-solid die-casting aluminum alloy are not more than 0.8 wt %.

5. The semi-solid die-casting aluminum alloy according to claim 1, wherein the ratio of the weight content of Ti to Cu is 1:(14 to 90).

6. The semi-solid die-casting aluminum alloy according to claim 4, wherein the semi-solid die-casting aluminum alloy comprises 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % Ti, 0.01 to 0.35 wt % of rare earth element, no more than 0.8 wt % of impurities and the balance of aluminum.

7. The semi-solid die-casting aluminum alloy according to claim 6, wherein the semi-solid die-casting aluminum alloy comprises 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % Ti, 0.15 to 0.25 wt % of rare earth element, no more than 0.7 wt % of impurities and the balance of aluminum.

8. The semi-solid die-casting aluminum alloy according to claim 1, wherein the semi-solid die-casting aluminum alloy has a tensile strength of not less than 370 MPa, a yield strength of not less than 290 MPa, and an elongation of not less than 5.5%.

9. The semi-solid die-casting aluminum alloy according to claim 2, wherein the semi-solid die-casting aluminum alloy has a tensile strength of not less than 380 MPa, a yield strength of not less than 300 MPa, and an elongation of not less than 6%.

10. A method for preparing a semi-solid die-casting aluminum alloy casting, comprising:

after performing ratio smelting on aluminum alloy raw materials, performing semi-solid die casting to obtain the semi-solid die-casting aluminum alloy casting,

wherein the aluminum alloy raw materials are such that the obtained semi-solid die-casting aluminum alloy casting comprises:

based on the total weight of the aluminum alloy casting, 7.5 to 9.5 wt % of Si, 3.5 to 4.8 wt % of Cu, 0.5 to 0.75 wt % of Mn, 0.01 to 0.5 wt % of Ti, 0.01 to 0.35 wt % of rare earth element, and the balance of aluminum and inevitable impurities.

11. The method according to claim 10, wherein the aluminum alloy raw materials are such that the obtained semi-solid die-casting aluminum alloy casting comprises: based on the total weight of the semi-solid die-casting aluminum alloy casting, 8.0 to 9.0 wt % of Si, 3.5 to 4.5 wt % of Cu, 0.5 to 0.6 wt % of Mn, 0.05 to 0.25 wt % of Ti, 0.15 to 0.25 wt % of rare earth element, and the balance of aluminum and inevitable impurities.

12. The method according to claim 10, wherein the aluminum alloy raw material is elemental metals or metal alloys.

13. The method according to claim 12, wherein the aluminum alloy raw materials are elemental aluminum or an alloy of aluminum, elemental silicon or an alloy of silicon, elemental copper or an alloy of copper, elemental manganese or an alloy of manganese, elemental titanium or an alloy of titanium, and an elemental rare earth element or an alloy containing a rare earth element.

14. The method according to claim 12, wherein the aluminum alloy raw materials are elemental aluminum, an Al—Si alloy, an Al—Ti alloy, an Al—Cu alloy, an Al—Mn alloy and an Al—Re intermediate alloy.

15. The method according to claim 12, wherein the purity of the elemental metal is 99.9 wt % or more, and the total content of the alloying elements in the metal alloy is 99.9 wt % or more.