A high-strength and tough cast aluminum alloy and its preparation method and application

Abstract

The present invention relates to a high-strength and toughness cast aluminum alloy and a preparation method and application thereof. The components of the high-strength and toughness cast aluminum alloy of the present invention are Si 4-10%, Cu 2-5%, Mg 0.3-2%, Fe 0.05-0.2%, Ti0.01-0.1%, Sb 0.02-0.1%, Bi 0.02-0.2% and Hf0.02-0.2%, and the rest is Al; the content of inevitable impurity elements is <0.15%. The high-strength and toughness cast aluminum alloy of the present invention is obtained by preheating and drying the raw materials, heating and melting in the form of pure metal or intermediate alloy, and then refining and solution heat treatment. The yield strength of the high-strength and toughness cast aluminum alloy prepared by the present invention is above 210MPa, the tensile strength is above 390MPa, and the elongation can reach above 12%; it effectively solves the problem of low strength and toughness of cast aluminum alloys and meets the needs of the automotive engineering field.

Description

Technical Field

[0001] The invention relates to the field of aluminum alloy materials, and in particular to a high-strength and toughness cast aluminum alloy and a preparation method and application thereof. Background Art

[0002] Aluminum alloy has a lower density and therefore has a lighter weight compared to other metals. This makes it an ideal choice for lightweighting in automotive, aviation and other applications, helping to improve fuel efficiency and reduce emissions. Among them, cast aluminum alloy has the advantages of good fluidity, good formability, good thermal conductivity, high production efficiency and low cost, and is widely used in the automotive field. It is often used in structures such as automobile bodies, wheels, fuel tanks, control arms, machine covers, motor housings, steering knuckles, push-pull rods, etc. However, gravity casting or low-pressure casting aluminum alloys have low mechanical properties such as strength and toughness. For example, traditional casting aluminum alloys such as ZL101 and ZL114 often have their strength increased at the expense of toughness, and it is difficult to meet the high-performance use requirements of modern automobiles such as large loads and large impacts. Therefore, improving the comprehensive mechanical properties of cast aluminum alloys is an urgent requirement for the current lightweight development of automobiles.

[0003] Chinese invention patent CN 116590583 A discloses a high-strength and toughness cast aluminum alloy and its preparation method. By adding Zr and rare earth elements such as Er, Ce, Y, and La, the alloy precipitates dispersed and fine nano-scale Al3 (RE, Zr) particles during heat treatment, which has a significant precipitation strengthening effect and improves the mechanical properties of the alloy. However, rare earth elements are relatively expensive, which leads to an increase in production costs.

[0004] Chinese patent CN 102127665 A introduces an Al-Zn-Mg-Cu-Sc-Zr-RE alloy that can be used as an ultra-high-strength cast aluminum alloy and its preparation method. The chemical composition of the alloy includes the following elements (by mass percentage): Zn 7.0-8.0%, Mg 1.5-2.5%, Cu 1.4-2.0%; Mn 0.2-0.5%; Sc 0.15-0.25%; Zr 0.10-0.20%; Er and / or Yb 0.1-0.3%, and the balance is Al. The casting alloy contains a high proportion of alloying elements, especially zinc, which increases the strength of the alloy, but also leads to poor casting performance of the alloy. In order to achieve appropriate toughness, long-term heat treatment is required, including temperature homogenization, strengthening solution treatment and aging treatment. These process steps are relatively complicated and are not suitable for large-scale industrial batch production.

[0005] Therefore, developing an economical, high-strength and toughness cast aluminum alloy that is not restricted by manufacturing process conditions to meet the actual use needs of castings in the automotive industry has become one of the goals pursued in the field of aluminum alloy casting. Summary of the invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a high-strength and toughness cast aluminum alloy and its preparation method and application, so as to solve one or more technical problems existing in the prior art. The invention is committed to achieving excellent comprehensive mechanical properties while ensuring that the alloy has good casting performance, thereby meeting the performance requirements of vehicle body structural parts.

[0007] To achieve the above-mentioned purpose, the present invention is implemented by the following technical solutions:

[0008] The first object of the present invention is to provide a high-strength and toughness casting alloy. The constituent elements of the high-strength and toughness casting alloy include, by weight percentage: Si 2% to 12%, Cu 1% to 5%, Mg 0.1% to 2%, Fe 0.05% to 0.3%, Ti 0.01% to 0.2%, Sb 0.02% to 0.1%, Bi 0.02% to 0.2%, Hf0.02% to 0.2%, and the rest is Al.

[0009] Preferably, the constituent elements of the high-strength and toughness casting alloy include: Si 4% to 10%, Cu 2% to 5%, Mg 0.3% to 2%, Fe 0.05% to 0.2%, Ti 0.01% to 0.1%, Sb 0.02% to 0.1%, Bi 0.02% to 0.2%, Hf 0.02% to 0.2%, and the rest is Al, and the content of unavoidable impurity elements is <0.15%.

[0010] In one embodiment of the present invention, the mass ratio of Sb:Bi:Hf is 1:2:2.

[0011] In one embodiment of the present invention, the solid solution amount of Cu element in the high-strength and toughness casting alloy is greater than 1wt%; the solid solution amount of Mg element is greater than 0.1wt%, wherein the solid solution amount refers to the content of these alloy elements in the alloy composition in the matrix.

[0012] In one embodiment of the present invention, the area fraction of the Al2Cu phase on the grain boundary of the high-strength and toughness casting alloy is less than 7%, and the area fraction of the Al5Cu2Mg7Si4 phase is less than 5%. The Al2Cu phase is bright white, and the Al5Cu2Mg7Si4 phase is light gray, and both are distributed along the grain boundary.

[0013] In one embodiment of the present invention, the size of the eutectic Si particles in the high-strength and toughness casting alloy is 1 μm to 10 μm; wherein the morphology of the eutectic Si particles is spherical or short rod-shaped.

[0014] In one embodiment of the present invention, the grain size of the high-strength and toughness casting alloy is 20 μm to 150 μm.

[0015] In one embodiment of the present invention, the size of the Fe-containing phase in the high-strength and toughness casting alloy is less than 20 μm; wherein the Fe-containing phase includes β-Al5FeSi, α-Al 15 (Fe,Mn)3Si2, etc.

[0016] The second object of the present invention is to provide a method for preparing a high-strength and tough cast aluminum alloy, comprising the following steps:

[0017] S1. After preheating and drying the raw materials, add them into a smelting furnace in the form of pure metal or master alloy, heat and melt them, and stir them evenly to obtain an alloy melt;

[0018] S2. In an atmosphere of protective gas, the alloy melt obtained in step S1 is mixed with a refining agent to perform refining, degassing and impurity removal; the refining agent is hexachloroethane.

[0019] S3. Casting and solution heat treating the melt obtained in step S2 to obtain a high-strength and toughness cast aluminum alloy.

[0020] In one embodiment of the present invention, one or more of the following conditions are met:

[0021] (1) In step S1, the drying temperature is 100° C. to 500° C.;

[0022] (2) In step S1, the melting temperature is 700° C. to 800° C. and the melting time is 5 min to 15 min;

[0023] (3) In step S3, the conditions of the solution heat treatment are: the temperature of the first stage is 470°C to 480°C, and the time is 1h to 3h; the temperature of the second stage is 490°C to 505°C, and the time is 1h to 6h; the temperature of the third stage is 510°C to 535°C, and the time is 1h to 6h.

[0024] The third object of the present invention is to provide application of the high-strength and toughness cast aluminum alloy in the field of automobile engineering.

[0025] The above technical solution of the present invention has the following advantages compared with the prior art:

[0026] The present invention provides a high-strength and toughness cast aluminum alloy and its preparation method and application. The present invention controls the alloy composition, ratio and preparation method, and reasonably sets the heat treatment process parameters to obtain one or more grains of a certain size and shape, eutectic Si particles, Fe-containing phases, and A12Cu phases and A15Cu2Mg7Si4 phases with a certain area fraction on the grain boundary, without destroying the toughness of the alloy to the greatest extent. At the same time, the solid solution of multiple alloy elements ensures good strength indicators and achieves high strength and high toughness. The yield strength of the cast aluminum alloy of the present invention is above 210MPa, the tensile strength is above 390MPa, and the elongation can reach above 12%. It effectively solves the problem of low strength and toughness of cast aluminum alloys and meets the needs of the automotive engineering field. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0028] Figure 1 The microstructure diagram of the cast aluminum alloy prepared in Example 1 of the present invention; wherein (a) is the OM structure of the solid solution alloy in Example 1; (b) is the SEM structure of the solid solution alloy in Example 1;

[0029] Figure 2 The microstructure diagram of the cast aluminum alloy prepared in Example 2 of the present invention; wherein (a) is the OM structure of the solid solution alloy in Example 2; (b) is the SEM structure of the solid solution alloy in Example 2;

[0030] Figure 3 The microstructure diagram of the cast aluminum alloy prepared in Example 3 of the present invention; wherein, (a) is the OM structure of the solid solution alloy in Example 3; (b) is the SEM structure of the solid solution alloy in Example 3. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0032] Example 1

[0033] The present embodiment discloses a high-strength and toughness cast aluminum alloy and a preparation method thereof. The components and weight percentages of the aluminum alloy are: Si 6.97%, Cu 2.03%, Mg 0.57%, Fe 0.085%, Ti 0.021%, Sb 0.03%, Bi 0.06%, Hf 0.06%, the balance being Al, and the content of unavoidable impurity elements being <0.15%.

[0034] The method for preparing the cast aluminum alloy based on the above composition in this embodiment comprises the following steps:

[0035] S1. Melting: Weigh the raw materials according to the designed composition and dry them in the furnace at 300℃. Add pure Al and Al-Si into the melting furnace and melt them at 730℃. After they are melted, add pure Mg and pure Cu, and stir them for 5 minutes after they are completely melted to obtain a uniform melt.

[0036] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining, the gas introduction rate is 0.1L / min, the refining time is 15min, and after standing for 5min, the slag is removed and impurities are removed.

[0037] S3. Forming: The refined aluminum alloy melt is subjected to gravity casting to obtain an aluminum alloy ingot.

[0038] S4. Heat treatment: The obtained casting is subjected to three-stage solution heat treatment, wherein the temperature of the first stage is 470°C and the time is 1h; the temperature of the second stage is 490°C and the time is 4h; the temperature of the third stage is 520°C and the time is 6h, followed by water cooling at a water temperature of 25°C.

[0039] The microstructure of the alloy prepared by the above method is as follows Figure 1 As shown. Through organizational observation, it is found that a large number of eutectic Si particles and some Al2Cu phases and Al5Cu2Mg7Si4 phases remaining after solution treatment are distributed in the alloy microstructure of this embodiment. According to statistics, the grain size range is 40μm-80μm, the size range of eutectic Si particles is 2μm-10μm, the area fractions of Al2Cu phase and Al5Cu2Mg7Si4 phase at the grain boundary are 0.35% and 0.33% respectively, and the size range of Fe-containing phase is 3μm-8μm.

[0040] Mechanical tensile tests were performed on the alloy plates, and the yield strength was 219 MPa, the tensile strength was 396 MPa, and the elongation was 18.63%.

[0041] Example 2

[0042] The present embodiment discloses a cast aluminum alloy and a preparation method thereof. The components and weight percentages of the aluminum alloy are: Si 6.4%, Cu 2.99%, Mg 0.57%, Fe 0.081%, Ti 0.023%, Sb 0.025%, Bi 0.051%, Hf0.05%, the balance being Al, and the content of unavoidable impurity elements being <0.15%.

[0043] The method for preparing the cast aluminum alloy based on the above composition in this embodiment comprises the following steps:

[0044] S1. Melting: Weigh the raw materials according to the designed composition and dry them in the furnace at 300℃. Add pure Al and Al-Si into the melting furnace and melt them at 730℃. After they are melted, add pure Mg and pure Cu, and stir them for 10 minutes after they are completely melted to obtain a uniform melt.

[0045] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining, the gas introduction rate is 0.1L / min, the refining time is 15min, and after standing for 5min, the slag is removed and impurities are removed.

[0046] S3. Forming: The refined aluminum alloy melt is cast into an aluminum alloy ingot by low-pressure casting.

[0047] S4. Heat treatment: The obtained casting is subjected to three-stage solution heat treatment, wherein the temperature of the first stage is 480°C and the time is 2h; the temperature of the second stage is 500°C and the time is 6h; the temperature of the third stage is 520°C and the time is 4h, followed by water cooling at a water temperature of 24°C.

[0048] The microstructure of the alloy prepared by the above method is as follows Figure 2 As shown. Through organizational observation, it is found that a large number of eutectic Si particles and some Al2Cu phases and Al5Cu2Mg7Si4 phases remaining after solution treatment are distributed in the alloy microstructure of this embodiment. According to statistics, the grain size range is 50μm-100μm, the size range of eutectic Si particles is 3μm-10μm, the area fractions of Al2Cu phase and Al5Cu2Mg7Si4 phase at the grain boundary are 1.38% and 0.57% respectively, and the size range of Fe-containing phase is 5μm-10μm.

[0049] Mechanical tensile tests were performed on the alloy plates, and the yield strength was 247.4 MPa, the tensile strength was 422.1 MPa, and the elongation was 12.2%.

[0050] Example 3

[0051] The present embodiment discloses a casting aluminum alloy and a preparation method thereof. The components and weight percentages of the aluminum alloy are: Si 6.93%, Cu 3.06%, Mg 0.57%, Fe 0.082%, Ti 0.023%, Sb 0.02%, Bi 0.04%, Hf 0.041%, the balance being Al, and the content of unavoidable impurity elements being <0.15%.

[0052] The method for preparing the cast aluminum alloy based on the above composition in this embodiment comprises the following steps:

[0053] S1. Melting: Weigh the raw materials according to the designed composition and dry them in the furnace at 300℃. Add pure Al and Al-Si into the melting furnace and melt them at 720℃. After they are melted, add pure Mg and pure Cu, and stir them for 5 minutes after they are completely melted to obtain a uniform melt.

[0054] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining, the gas introduction rate is 0.1L / min, the refining time is 15min, and after standing for 5min, the slag is removed and impurities are removed.

[0055] S3. Forming: The refined aluminum alloy melt is cast into an aluminum alloy ingot by low-pressure casting.

[0056] S4. Heat treatment: The obtained casting is subjected to three-stage solution heat treatment, wherein the temperature of the first stage is 480°C and the time is 2h; the temperature of the second stage is 500°C and the time is 4h; the temperature of the third stage is 520°C and the time is 6h, followed by water cooling at 20°C.

[0057] The microstructure of the alloy prepared by the above method is as follows Figure 3 As shown. Through organizational observation, it was found that a large number of eutectic Si particles and some Al2Cu phases and Al5Cu2Mg7Si4 phases remaining after solution treatment were distributed in the alloy microstructure of this embodiment. According to statistics, the grain size range is 40-100μm, the size range of eutectic Si particles is 2-10μm, the area fractions of Al2Cu phase and Al5Cu2Mg7Si4 phase at the grain boundary are 1.32% and 0.53% respectively, and the size range of Fe-containing phase is 2-8μm. The alloy plate was subjected to mechanical tensile test, and its yield strength was 256.4MPa, the tensile strength was 440.9MPa, and the elongation was 16.6%.

[0058] Comparative Example 1

[0059] This comparative example discloses a cast aluminum alloy and a preparation method thereof. The components and weight percentages of the aluminum alloy are: Si 6.4%, Cu 2.99%, Mg 0.57%, Fe 0.081%, Ti 0.023%, Sb 0.025%, Bi 0.051%, Hf 0.05%, the balance being Al, and the content of unavoidable impurity elements being <0.15%.

[0060] The preparation method of the cast aluminum alloy based on the above composition in this comparative example comprises the following steps:

[0061] S1. Melting: Weigh the raw materials according to the designed composition and dry them in the furnace at 300℃. Add pure Al and Al-Si into the melting furnace and melt them at 730℃. After they are melted, add pure Mg and pure Cu, and stir them for 10 minutes after they are completely melted to obtain a uniform melt.

[0062] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining, the gas introduction rate is 0.1L / min, the refining time is 15min, and after standing for 5min, the slag is removed and impurities are removed.

[0063] S3. Forming: The refined aluminum alloy melt is cast into an aluminum alloy ingot by low-pressure casting.

[0064] S4. Heat treatment: subject the obtained casting to solution heat treatment at 500°C for 8h, followed by water cooling at 24°C.

[0065] The alloy plate was subjected to mechanical tensile test, and its yield strength was 221.4MPa, tensile strength was 360.1MPa, and elongation was 7.2%.

[0066] Comparative Example 2

[0067] This comparative example discloses a casting aluminum alloy and a preparation method thereof. The components and weight percentages of the aluminum alloy are: Si 6.93%, Cu 3.06%, Mg 0.57%, Fe 0.082%, Ti 0.023%, Bi 0.04%, the balance being Al, and the content of inevitable impurity elements being <0.15%.

[0068] The preparation method of the cast aluminum alloy based on the above composition in this comparative example comprises the following steps:

[0069] S1. Melting: Weigh the raw materials according to the designed composition and dry them in the furnace at 300℃. Add pure Al and Al-Si into the melting furnace and melt them at 720℃. After they are melted, add pure Mg and pure Cu, and stir them for 5 minutes after they are completely melted to obtain a uniform melt.

[0070] S2. Refining: Hexachloroethane gas is introduced into the aluminum alloy melt for refining, the gas introduction rate is 0.1L / min, the refining time is 15min, and after standing for 5min, the slag is removed and impurities are removed.

[0071] S3. Forming: The refined aluminum alloy melt is cast into an aluminum alloy ingot by low-pressure casting.

[0072] S4 heat treatment: The obtained casting is subjected to three-stage solution heat treatment, wherein the temperature of the first stage is 480°C and the time is 2h; the temperature of the second stage is 500°C and the time is 4h; the temperature of the third stage is 520°C and the time is 6h, followed by water cooling at 20°C.

[0073] Mechanical tensile tests were performed on the alloy plates, and the yield strength was 215.4 MPa, the tensile strength was 370.9 MPa, and the elongation was 6.6%.

[0074] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A high-strength and tough cast aluminum alloy, characterized in that: In terms of weight percentage, the components of the high-strength and toughness cast aluminum alloy include Si 2% to 12%, Cu 1% to 5%, Mg 0.1% to 2%, Fe 0.05% to 0.3%, Ti 0.01% to 0.2%, Sb 0.02% to 0.1%, Bi 0.02% to 0.2%, Hf 0.02% to 0.2%, and the rest is Al; The mass ratio of Sb:Bi:Hf is 1:2:2; The area fraction of the Al2Cu phase on the grain boundary of the high-strength and toughness cast aluminum alloy is less than 7%, and the area fraction of the Al5Cu2Mg7Si4 phase is less than 5%; The size of the eutectic Si particles in the high-strength and toughness cast aluminum alloy is 1 μm to 10 μm; The grain size of the high-strength and toughness cast aluminum alloy is 20 μm to 150 μm; The size of the Fe-containing phase in the high-strength and toughness cast aluminum alloy is less than 20 μm; The high-strength and toughness cast aluminum alloy has a yield strength of more than 210 MPa, a tensile strength of more than 390 MPa, and an elongation of more than 12%.

2. The high-strength and toughness cast aluminum alloy according to claim 1, characterized in that: The solid solution amount of Cu element in the high-strength and toughness cast aluminum alloy is greater than 1wt%; the solid solution amount of Mg element is greater than 0.1wt%.

3. The method for preparing the high-strength and toughness cast aluminum alloy according to claim 1 or 2, characterized in that: The following steps are involved: S1. After preheating and drying the raw materials, add them into a smelting furnace in the form of pure metal or master alloy, heat and melt them, and stir them evenly to obtain an alloy melt; S2, in an atmosphere of protective gas, mixing the alloy melt obtained in step S1 with a refining agent, and performing refining, degassing and impurity removal; S3. Casting and solution heat treating the melt obtained in step S2 to obtain a high-strength and toughness cast aluminum alloy.

4. The preparation method according to claim 3, characterized in that: One or more of the following conditions are met: (1) In step S1, the drying temperature is 100°C to 300°C; (2) In step S1, the melting temperature is 700°C to 800°C and the melting time is 5 min to 15 min; (3) In step S3, the conditions of the solution heat treatment are: the temperature of the first stage is 470°C~480°C, and the time is 1h~3h; the temperature of the second stage is 490°C~505°C, and the time is 1h~6h; the temperature of the third stage is 510°C~535°C, and the time is 1h~6h.

5. Application of the high-strength and toughness cast aluminum alloy according to any one of claims 1 or 2 in the field of automotive engineering.

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