A cast aluminum alloy and a preparation method thereof

Abstract

The present invention belongs to the field of aluminum alloys, and particularly relates to a cast aluminum alloy and a preparation method thereof. The composition of the aluminum alloy is as follows: Mg 4-8%, Si 1-6%, Fe 0.1-0.5%, Cu 0.5%-3%, Zn 0.5-1.5%, Mn 0.1-0.5%, Mo 0.01-0.1%, V 0.01-0.1%, Sr 0.01-0.03%, and the balance is Al and inevitable impurity elements. The cast aluminum alloy contains Si, AlMg, α-Fe, Al5Cu2Mg8Si6, Mg2Si and Al2Cu phases. The preparation method of the aluminum alloy is casting forming and heat treatment. The yield strength of the cast aluminum alloy is 270-320 MPa, the tensile strength is 330-380 MPa, and the elongation is 6%-10%. The cast aluminum alloy and the preparation method thereof according to the present invention realize the simultaneous improvement of the formability, strength and toughness, and corrosion resistance of the Al-Mg alloy.

Description

Technical Field

[0001] The present invention belongs to the field of aluminum alloy materials, and particularly relates to a cast aluminum alloy and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, aluminum alloy castings have been more widely used in automobile bodies and components. With the improvement of the safety performance of automobile structural parts, higher requirements have been put forward for the strength and toughness of aluminum alloys. Traditional cast Al-Si aluminum alloys are gradually difficult to meet the usage requirements of modern automobiles, and it is urgent to improve the comprehensive mechanical properties of cast aluminum alloys. Since the mechanical properties of Al-Mg alloys are superior to those of Al-Si cast alloys, they are ideal materials to replace Al-Si alloys for preparing automobile bodies and automobile components. However, due to the low fluidity of Al-Mg alloys and their inability to be heat-treated and strengthened, their application scope is limited.

[0003] Chinese invention patent CN 118531268A discloses a high-strength and tough cast Al-Mg alloy and a preparation method thereof. The invention prepares the alloy by an squeeze casting method and quenches it using the waste heat of pressure casting, thereby improving the strength and toughness of the alloy. This invention is only applicable to the squeeze casting method, which limits the forming method of the alloy. Moreover, this alloy cannot be heat-treated and strengthened, and its strength improvement effect is limited. The yield strength of the alloy does not exceed 165 Mpa, greatly limiting the application scope of the alloy.

[0004] Chinese invention patent CN110603341A discloses a high-strength and tough cast Al-Mg alloy and a preparation method thereof. By adding elements such as Zr, Sc, Hf, V, and Cr to the Al-Mg alloy, the strength and toughness of the alloy are effectively improved. However, the addition of the above elements will undoubtedly increase the production cost of components. At the same time, this alloy cannot be strengthened by heat treatment, and the strength improvement effect is limited. Summary of the Invention

[0005] The cast aluminum alloys and their preparation methods disclosed in the above patents improve the strength and toughness of the alloys to a certain extent, but they do not change the characteristics that the alloys cannot be heat-treated and strengthened. How to significantly improve the strength of cast aluminum alloys is of great significance for enhancing the safety of automobile components.

[0006] In order to solve the above existing technical problems, the present application provides the following technical solutions:

[0007] The present invention provides a cast aluminum alloy, in which

[0008] the volume fraction of eutectic Si is 0.01 - 2.2%; in the non-heat-treated state, the eutectic Si is in a fibrous morphology, and the diameter of a single eutectic Si fiber is less than 3 μm; the volume fraction of the AlMg phase is 3 - 18%;

[0009] The volume fraction of the Fe-containing phase in α-Al(FeM)Si is 0.1-2.3%, and the size is 200-500 nm; where M is selected from one or more of Mn, Mo, and V; the volume fraction of the Al5Cu2Mg8Si6 phase is 0.1-5.8%, and the size is not more than 10 μm;

[0010] The mass ratio of Mg to Si is greater than 1.3, and the volume fraction of the Mg2Si phase is 3-14%; the volume fraction of the Al2Cu phase is 0.1-1.8%.

[0011] Preferably, by weight fraction, the composition of the aluminum alloy comprises 4-8% of Mg, 1-6% of Si, 0.1-0.5% of Fe, 0.5%-3% of Cu, 0.5-1.5% of Zn, 0.01-0.5% of Mn, 0.01-0.1% of Mo, 0.01-0.1% of V, 0.01-0.03% of Sr, and the balance is Al and inevitable impurity elements.

[0012] The present invention also provides a preparation method of the above-cast aluminum alloy, comprising the following steps:

[0013] S11: Using pure Al, pure Mg, Al-20Si, Al-10Fe, pure Cu, pure Zn, Al-10Mn master alloy, Al-5Mo master alloy, Al-5V master alloy, and Al-10Sr master alloy as raw materials for batching and melting to obtain an aluminum alloy ingot; by weight fraction, the composition of the aluminum alloy ingot comprises 4-8% of Mg, 1-6% of Si, 0.1-0.5% of Fe, 0.5%-3% of Cu, 0.5-1.5% of Zn, 0.01-0.5% of Mn, 0.01-0.1% of Mo, 0.01-0.1% of V, 0.01-0.03% of Sr, and the balance is Al and inevitable impurity elements;

[0014] S12: Performing solution treatment and aging treatment on the aluminum alloy ingot to obtain the cast aluminum alloy.

[0015] Preferably, casting is performed after melting, and the casting method is selected from gravity casting, high-pressure casting, squeeze casting, low-pressure casting, or differential pressure casting.

[0016] Preferably, in the step S12, the solution treatment comprises the following steps:

[0017] S21: Placing the aluminum alloy ingot in a heat treatment furnace, heating to 480-500 °C and holding for 6-10 h;

[0018] S22: Heating to 510-530 °C and holding for 1-8 h;

[0019] S23: Perform water quenching treatment to complete the solution treatment step.

[0020] Furthermore, in the step S21, the temperature is increased at a heating rate of 40 - 110 °C per hour.

[0021] Preferably, in the step S12, the yield strength of the aluminum alloy ingot after solution + aging treatment is 270 - 320 MPa.

[0022] Preferably, in the step S12, the tensile strength of the aluminum alloy ingot after solution + aging treatment is 330 - 380 MPa.

[0023] Preferably, in the step S12, the elongation of the aluminum alloy ingot after solution + aging treatment is 6% - 10%.

[0024] Preferably, in the step S12, the aging treatment includes the following steps: aging the solution-treated alloy ingot at 160 - 190 °C for 15 - 22 h to obtain the cast aluminum alloy.

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

[0026] The present invention relates to a cast aluminum alloy and a preparation method thereof. By controlling the alloy composition and ratio, as well as the temperature and time of heat treatment during the preparation process, the eutectic Si volume fraction, the α-Al(FeM)Si Fe-containing phase (where M is one or more of Mn, Mo, V), the volume fractions and sizes of the Al5Cu2Mg8Si6 phase and the Al2Cu phase are regulated, so as to simultaneously improve the strength and toughness, fluidity and corrosion resistance of the Al-Mg alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the alloy structure of Example 1 of the present invention;

[0028] Figure 2 It is a schematic diagram of the alloy structure of Example 2 of the present invention;

[0029] Figure 3 It is a schematic diagram of the alloy structure of Example 3 of the present invention;

[0030] Figure 4 It is a schematic diagram of the alloy structure of Example 4 of the present invention;

[0031] Figure 5 It is a schematic diagram of the alloy structure of Example 5 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be 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 be able to implement it, but the embodiments cited are not intended to limit the present invention. Example 1

[0033] A cast aluminum alloy and its preparation method disclosed in this embodiment have high strength and high toughness, and at the same time, fluidity and corrosion resistance are also improved. The components of the aluminum alloy and their respective weight percentages are: Mg 4%, Si 1%, Fe 0.1%, Cu 0.5%, Zn 0.5%, Mn 0.1%, Mo 0.01%, V 0.01%, Sr 0.01%, and the rest are Al and inevitable impurity elements.

[0034] The preparation method of the high-toughness cast aluminum alloy based on the above components in this embodiment includes the following steps:

[0035] (1) Weigh and melt the aluminum alloy with the above components, and obtain an ingot through gravity casting;

[0036] (2) Perform solution treatment and aging treatment on the ingot in step (1):

[0037] First, place the aluminum alloy ingot in a heat treatment furnace, heat the ingot from room temperature (25°C) to 480°C at a rate of 40°C per hour, hold for 6 h, then heat to 510°C and hold for 1 h, and after completion, perform water quenching treatment;

[0038] Keep the solution-treated alloy ingot at 160°C for 15 h to finally obtain a high-toughness cast aluminum alloy.

[0039] The mass percentage of Mg and Si in the alloy of this embodiment is 4%. The alloy structure obtained in this embodiment is as Figure 1 shown. Through microstructure observation under a scanning electron microscope, it is found that the Fe-containing phase in the as-cast aluminum alloy contains α-Al(FeMn)Si, α-Al(FeMo)Si, and α-Al(FeV)Si. The volume fraction range of the Fe-containing phase is 0.3%, and the size is about 200 nm; the volume fraction of the Mg2Si phase is 3.1%; the volume fraction of the Al2Cu phase is 0.18%; the volume fraction of the AlMg phase is 6%.

[0040] After tensile property testing (testing standard GB / T6397-1985), the yield strength of the cast aluminum alloy is 272 MPa, the tensile strength is 336 MPa, and the elongation is 6.2%. Example 2

[0041] A kind of cast aluminum alloy and its preparation method disclosed in this embodiment have high strength and high toughness, and at the same time, fluidity and corrosion resistance are also improved. The components of the aluminum alloy and their respective weight percentages are: Mg 5%, Si 2.5%, Fe 0.2%, Cu 1%, Zn 0.7%, Mn 0.2%, Mo 0.03%, V 0.03%, Sr 0.01%, and the rest are Al and inevitable impurity elements.

[0042] The preparation method of the high-toughness cast aluminum alloy based on the above components in this embodiment includes the following steps:

[0043] (1) Weigh and melt the aluminum alloy with the above components, and obtain an ingot through gravity casting;

[0044] (2) Perform solution treatment and aging treatment on the ingot in step (1):

[0045] First, place the aluminum alloy ingot in a heat treatment furnace, heat the ingot from room temperature to 485°C at a rate of 60°C per hour, hold for 7 h, then heat up to 515°C and hold for 3 h, and after completion, perform water quenching treatment;

[0046] Keep the alloy ingot after solution treatment at 170°C for 16 h to finally obtain a high-toughness cast aluminum alloy.

[0047] In this embodiment, the mass percentage of Mg and Si in the alloy is 2%. The alloy structure obtained in this embodiment is as Figure 2 shown. Through microstructure observation under a scanning electron microscope, it is found that the Fe-containing phase in the as-cast aluminum alloy contains α-Al(FeMn)Si, α-Al(FeMo)Si, and α-Al(FeV)Si. The volume fraction range of the Fe-containing phase is 0.5%, and the size is about 270 nm; the volume fraction range of the Al5Cu2Mg8Si6 phase is 0.43%, and the size is about 10 μm; the volume fraction of the Mg2Si phase is 7%; the volume fraction of the Al2Cu phase is 0.1%; the volume fraction of the AlMg phase is 18%.

[0048] After tensile property testing (testing standard GB / T6397-1985), the yield strength of the cast aluminum alloy is 287 MPa, the tensile strength is 347 MPa, and the elongation is 7.4%. Example 3

[0049] A kind of cast aluminum alloy and its preparation method disclosed in this embodiment have high strength and high toughness, and at the same time, fluidity and corrosion resistance are also improved. The components and weight percentages of the aluminum alloy are as follows: Mg 6.5%, Si 3%, Fe 0.3%, Cu 2%, Zn 1%, Mn 0.3%, Mo 0.05%, V 0.05%, Sr 0.02%, and the rest are Al and inevitable impurity elements.

[0050] The preparation method of the cast aluminum alloy based on the above components in this embodiment includes the following steps:

[0051] (1) Weigh and melt the aluminum alloy, and obtain an ingot through squeeze casting;

[0052] (2) Carry out solution treatment and aging treatment on the ingot in step (1):

[0053] First, place the aluminum alloy ingot in a heat treatment furnace, heat the ingot from room temperature to 490 °C at a rate of 80 °C per hour, hold for 8 h, then heat up to 520 °C and hold for 5 h, and after completion, carry out water quenching treatment;

[0054] Keep the alloy ingot after solution treatment at 175 °C for 19 h to finally obtain a high-toughness cast aluminum alloy.

[0055] The mass percentage of Mg and Si in the alloy of this embodiment is 2.2%. The alloy structure obtained in this embodiment is as Figure 3 shown. Through microstructure observation under a scanning electron microscope, it is found that the Fe-containing phase in the non-heat-treated state of the cast aluminum alloy includes α-Al(FeMn)Si, α-Al(FeMo)Si, and α-Al(FeV)Si. The volume fraction range of the Fe-containing phase is 1.1%, and the size is about 350 nm; the volume fraction range of the Al5Cu2Mg8Si6 phase is 0.8%, and the size is about 8 μm; the volume fraction of the Mg2Si phase is 9.7%; the volume fraction of the Al2Cu phase is 0.8%; the volume fraction of the AlMg phase is 12%.

[0056] After tensile property testing (testing standard GB / T6397-1985), the yield strength of the cast aluminum alloy is 299 MPa, the tensile strength is 365 MPa, and the elongation is 8.7%. Example 4

[0057] A kind of cast aluminum alloy and its preparation method disclosed in this embodiment have high strength and high toughness, and at the same time, fluidity and corrosion resistance are also improved. The components and weight percentages of the aluminum alloy are as follows: Mg 7%, Si 5%, Fe 0.4%, Cu 2.5%, Zn 1.3%, Mn 0.4%, Mo 0.07%, V 0.07%, Sr 0.03%, and the rest are Al and inevitable impurity elements.

[0058] The preparation method of the high-toughness cast aluminum alloy based on the above components in this embodiment includes the following steps:

[0059] (1) Weigh and melt the aluminum alloy with the above components, and obtain an ingot through gravity casting;

[0060] (2) Perform solution treatment and aging treatment on the ingot in step (1):

[0061] First, place the aluminum alloy ingot in a heat treatment furnace, heat the ingot from room temperature to 495°C at a rate of 100°C per hour and hold for 9 h, then heat it to 525°C and hold for 7 h, and after completion, perform water quenching treatment;

[0062] Keep the solution-treated alloy ingot at 180°C for 21 h to finally obtain a high-toughness cast aluminum alloy.

[0063] The mass percentage of Mg and Si in the alloy of this embodiment is 1.4. The alloy structure obtained in this embodiment is as Figure 4 shown. Through microstructure observation under a scanning electron microscope, it is found that the volume fraction range of eutectic Si in the matrix of the cast aluminum alloy in the non-heat-treated state is 2.2%, the morphology is fibrous, the Fe-containing phase includes α-Al(FeMn)Si, α-Al(FeMo)Si, and α-Al(FeV)Si, the volume fraction range of the Fe-containing phase is 1.6%, and the size is about 400 nm; the volume fraction range of the Al5Cu2Mg8Si6 phase is 5.9%, and the size is about 10 μm; the volume fraction of the Mg2Si phase is 10%; the volume fraction of the Al2Cu phase is 0.13%.

[0064] After tensile property testing (testing standard GB / T6397 - 1985), the yield strength of the cast aluminum alloy is 310 MPa, the tensile strength is 370 MPa, and the elongation is 9.2%. Example 5

[0065] A cast aluminum alloy and its preparation method disclosed in this embodiment have high strength and high toughness, and at the same time, fluidity and corrosion resistance are also improved. The components and weight percentages of the aluminum alloy are: Mg 8%, Si 6%, Fe 0.5%, Cu 3%, Zn 1.5%, Mn 0.5%, Mo 0.1%, V 0.1%, Sr 0.03%, and the rest are Al and inevitable impurity elements.

[0066] The preparation method of the high-toughness cast aluminum alloy based on the above components in this embodiment includes the following steps:

[0067] (1) Weigh and melt the aluminum alloy, and obtain an ingot through high pressure;

[0068] (2) Perform solution treatment and aging treatment on the ingot in step (1):

[0069] Place the aluminum alloy ingot in a heat treatment furnace, heat the ingot from room temperature to 500 °C at a rate of 110 °C per hour and hold for 10 h, then heat it to 530 °C and hold for 8 h, and perform water quenching treatment after completion;

[0070] Keep the alloy ingot after solution treatment at 190 °C for 22 h to finally obtain a high-toughness cast aluminum alloy.

[0071] The mass percentage of Mg and Si in the alloy of this embodiment is 1.3. The alloy structure obtained in this embodiment is as Figure 5 shown. Through microstructure observation under a scanning electron microscope, it is found that the volume fraction range of eutectic Si in the matrix of the cast aluminum alloy in the non-heat-treated state is 0.8%, and the morphology is fibrous. The Fe-containing phase includes α-Al(FeMn)Si, α-Al(FeMo)Si, and α-Al(FeV)Si. The volume fraction range of the Fe-containing phase is 2.3%, and the size is about 500 nm; the volume fraction range of the Al5Cu2Mg8Si6 phase is 2.2%, and the size is about 6 μm; the volume fraction of the Mg2Si phase is 14%; the volume fraction of the Al2Cu phase is 1.8%; the volume fraction of the AlMg phase is 3%.

[0072] After tensile property testing (testing standard GB / T6397-1985), the yield strength of the cast aluminum alloy is 323 MPa, the tensile strength is 382 MPa, and the elongation is 10.1%.

[0073] The technical content and technical features of the present invention have been disclosed above. However, those skilled in the art may still make various substitutions and modifications that do not deviate from the spirit of the present invention based on the teachings and disclosures of the present invention. Therefore, the protection scope of the present invention should not be limited to the content disclosed in the embodiments, but should include various substitutions and modifications that do not deviate from the present invention and are covered by the claims of this patent application.

Claims

1. A cast aluminum alloy, characterized in that, In the cast aluminum alloy, the volume fraction of eutectic Si is 0.01 - 2.2%; in the non-heat-treated state, the eutectic Si is in a fibrous morphology, and the diameter of a single eutectic Si fiber is less than 3 μm; the volume fraction of the AlMg phase is 3 - 18%; the α-Fe phase is the α-Al(FeM)Si phase, with a volume fraction of 0.1 - 2.3% and a size of 200 - 500 nm; where M is selected from Mn, Mo, and V; the volume fraction of the Al5Cu2Mg8Si6 phase is 0.1 - 5.8% and the size is not greater than 10 μm; the mass ratio of Mg to Si is greater than 1.3, and the volume fraction of the Mg2Si phase is 3 - 14%; the volume fraction of the Al2Cu phase is 0.1 - 1.8%; by weight fraction, the composition of the aluminum alloy includes 4 - 8% Mg, 1 - 6% Si, 0.1 - 0.5% Fe, 0.5% - 3% Cu, 0.5 - 1.5% Zn, 0.01 - 0.5% Mn, 0.01 - 0.1% Mo, 0.01 - 0.1% V, 0.01 - 0.03% Sr, and the balance is Al and unavoidable impurity elements.

2. The preparation method of the cast aluminum alloy according to claim 1, characterized in that, It includes the following steps: S11: Using pure Al, pure Mg, Al-20Si, Al-10Fe, pure Cu, pure Zn, Al-10Mn master alloy, Al-5Mo master alloy, Al-5V master alloy, and Al-10Sr master alloy as raw materials for batching and melting to obtain an aluminum alloy ingot; by weight fraction, the composition of the aluminum alloy ingot includes 4 - 8% Mg, 1 - 6% Si, 0.1 - 0.5% Fe, 0.5% - 3% Cu, 0.5 - 1.5% Zn, 0.01 - 0.5% Mn, 0.01 - 0.1% Mo, 0.01 - 0.1% V, 0.01 - 0.03% Sr, and the balance is Al and unavoidable impurity elements; S12: Performing solution treatment and aging treatment on the aluminum alloy ingot to obtain the cast aluminum alloy; In the step S12, the aging treatment includes the following steps: keeping the alloy ingot after solution treatment at 160 - 190 °C for 15 - 22 h to obtain the cast aluminum alloy; In the step S12, the solution treatment includes the following steps: S21: Placing the aluminum alloy ingot in a heat treatment furnace, heating it to 480 - 500 °C and keeping it for 6 - 10 h; S22: Heating it to 510 - 530 °C and keeping it for 1 - 8 h; S23: Performing water quenching treatment to complete the solution treatment step.

3. The preparation method according to claim 2, wherein, After melting, casting is carried out, and the casting method is selected from gravity casting, high-pressure casting, squeeze casting, low-pressure casting, or differential pressure casting.

4. The preparation method according to claim 2, characterized in that, In the step S21, the heating is carried out at a heating rate of 40 - 110 °C per hour.

5. The preparation method according to claim 2, characterized in that, In the step S12, the yield strength of the cast aluminum alloy is 270 - 320 MPa.

6. The preparation method according to claim 2, wherein In the step S12, the tensile strength of the cast aluminum alloy is 330 - 380 MPa.

7. The preparation method according to claim 2, characterized in that, In the step S12, the elongation rate of the cast aluminum alloy is 6% - 10%.

Images