A die-cast aluminum alloy having high electrical conductivity and high strength and a method for producing the same

Abstract

The application discloses a die-casting aluminum alloy with high conductivity and high tenacity, which is composed of the following raw materials in percentage by weight: Fe: <=0.3wt%, Si: 0.1-0.4wt%, Ce: <=1.5wt%, La: <=0.5wt%, Ni: <=4.0wt%, Zr: 0.05-0.3wt%, B: 0.05-0.15wt%, Mg: 0.05-0.4wt%, Cu <=0.2wt%, Mn+Cr+Ti+V <=0.1wt%, the balance of Al and inevitable impurities, and the sum of the weight percentage of the impurities is controlled to be below 0.1wt%. The application has the beneficial effect that the material has high conductivity and high tenacity.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of die-casting aluminum alloy processing, in particular to a die-casting aluminum alloy with high electrical conductivity and high strength and toughness and a preparation method thereof. BACKGROUND

[0002] The new energy industry is developing rapidly, and the lightweight demand brought by new energy has greatly expanded the consumption growth space of aluminum products. Aluminum has excellent electrical conductivity and thermal conductivity, is rich in resources and low in cost, and has obvious advantages in the field of automobile lightweight. At the present stage, more and more automobile enterprises use aluminum materials to replace copper materials as the motor rotor of new energy vehicles to achieve the purpose of cost saving and lightweight;

[0003] Although aluminum has obvious advantages, it has poor strength and unsatisfactory die-casting performance, and usually needs to add other alloying elements to enhance the die-casting and mechanical properties of aluminum. However, the added metal elements cannot simultaneously consider the die-casting property, electrical conductivity and mechanical property, and there is always a contradictory change rule, thus limiting the application of the die-casting aluminum alloy;

[0004] Patent CN114318085A discloses an aluminum alloy with excellent mechanical properties, electrical conductivity and thermal conductivity and a manufacturing method thereof. The aluminum alloy comprises 0.33-0.37 wt% of silicon elements, 0.45-0.55 wt% of magnesium elements and 0.07-0.15 wt% of iron elements, further comprises less than or equal to 0.03 wt% of gallium elements, less than or equal to 0.03 wt% of zinc elements, less than or equal to 0.01 wt% of manganese elements, less than or equal to 0.01 wt% of titanium elements, less than or equal to 0.001 wt% of sodium elements, less than or equal to 0.0002 wt% of lithium elements, less than or equal to 0.015 wt% of the sum of the manganese elements, vanadium elements and chromium elements, less than or equal to 0.01 wt% of other elements, and the total content of the above elements in the aluminum alloy is less than or equal to 0.1 wt%, and the rest is aluminum elements. The mass ratio of the difference between the magnesium elements and one-third of the silicon elements and the iron elements is 1.45-1.75. In the patent, the main elements are Mg, Si and Fe, and the strengthening is mainly carried out through Mg2Si strengthening phase. The patent alloy lacks high-temperature stabilizing elements, and the Mg2Si strengthening phase will coarsen when the material is used at a high temperature for a long time, resulting in performance attenuation. In addition, the alloy composition also lacks elements for improving fluidity, and the contents of Si, Mg and Fe for reducing the sticking tendency are also limited at a low level, which means that it is difficult to carry out die-casting in the actual production process, the porosity cannot be guaranteed, and the application has certain limitations;

[0005] Patent 114318090B discloses a new energy vehicle motor rotor casting aluminum alloy and its preparation method, which comprises titanium 0.05wt%-0.06wt%, boron 0.04wt%-0.06wt%, silicon 0.15wt%-0.5wt, iron 0.01wt%-0.08wt%, copper 0.5wt%-0.7wt%, magnesium 0.3wt%-0.5wt%, zinc 0.01wt%-0.2wt%, manganese 0.02wt%-0.12wt%, and the rest is aluminum. The patent also ensures the mechanical properties and electrical conductivity of the material at room temperature through element adjustment, and Cu is added to improve the high temperature performance; the addition of Cu alloy element to improve the strength will sacrifice the electrical conductivity of the material, which is not conducive to the improvement of the electrical conductivity, and the addition of too high content of Cu element significantly widens the solid-liquid phase interval, increases the risk of thermal cracking of the material during casting, and is difficult to apply to die casting.

[0006] In view of the above, it is necessary to improve the existing preparation method of high-conductivity aluminum alloy, so that it can adapt to the needs of the use of die-casting aluminum alloy at present, improve the production efficiency while considering the performance, and meet the performance requirements of motor rotor or other high-conductivity applications. SUMMARY

[0007] The purpose of the present application is to solve the above problems, and a die-casting aluminum alloy with high electrical conductivity and high strength and a preparation method thereof are designed.

[0008] The technical scheme for achieving the above-mentioned purpose is a die-casting aluminum alloy with high electrical conductivity and high strength, which is composed of the following raw materials in percentage by weight: Fe:≤0.3wt%, Si:0.1-0.4wt%, Ce:≤1.5wt%, La:≤0.5wt%, Ni:≤4.0wt%, Zr:0.05-0.3wt%, B:0.05-0.15wt%, Mg:0.05-0.4wt%, Cu≤0.2wt%, Mn+Cr+Ti+V≤0.1wt%, and the balance is Al and unavoidable impurities, and the sum of the weight percentage of impurities is controlled to be below 0.1wt%.

[0009] Further supplement to the technical scheme, the Zr and La, Ce are added in the form of fine-grained alloy.

[0010] Further supplement to the technical scheme, the fine-grained alloy is prepared by high-speed gas quenching method combined with planetary high-energy mechanical ball milling method to treat Al-Zr, Al-La and Al-Ce to obtain fine-grained alloy powder.

[0011] Further supplement to the technical scheme, the high-speed gas quenching method combined with planetary high-energy mechanical ball milling method includes the following working steps:

[0012] Step one: adding Al-Zr, Al-La and Al-Ce intermetallic alloy respectively, specifically, the mass distribution is matched according to the component requirements to obtain the preset composition of the intermetallic alloy;

[0013] Step two: heating the preset composition intermetallic alloy to 950-1200℃ molten state by an induction heater;

[0014] Step three: forming small droplets by high-speed inert gas flow impact on the molten stream, and collecting the mixed fine-grained alloy powder after rapid cooling;

[0015] Step four: placing the mixed fine-grained alloy powder in a planetary high-energy ball mill under inert gas atmosphere protection for intermittent ball milling to promote further transformation of the alloy, and finally obtaining the required fine-grained alloy.

[0016] Further supplement to the technical solution, the gas flow in the high-speed gas rapid cooling method is helium, and the gas flow pressure is 3-8Mpa; the ball milling time in the high-energy mechanical ball milling method is 20-60h, the ratio of running time to stopping time is 5:1, and the ball milling speed is 300-500r / min.

[0017] A preparation method of a die-casting aluminum alloy with high electrical conductivity and high strength and toughness, comprising the following steps:

[0018] 1) According to the proportion of alloy composition, first put high-purity aluminum elements into a heating furnace, heat to 690℃, completely melt and keep for 15min;

[0019] 2) Heating to 760℃, adding Si, Cu elemental and Al-Fe alloy;

[0020] 3) Cooling to 730℃, adding Al-B, Al-Ni intermetallic alloy and Al-Zr-La-Ce fine-grained alloy;

[0021] 4) Cooling to 720℃, adding pure Mg metal material;

[0022] 5) After the raw materials are completely melted, the melt is refined and degassed, and finally the aluminum alloy ingot is obtained by casting.

[0023] Further supplement to the technical solution, the aluminum alloy casting is subjected to high-pressure die casting forming.

[0024] Further supplement to the technical solution, the high-pressure die casting forming working steps are as follows:

[0025] 1) Melting the aluminum alloy ingot at 740℃ again and keeping;

[0026] 2) When keeping, protective gas is introduced to isolate from air, and then the die casting mold is injected;

[0027] 3) The molten alloy obtained in step 1) is pre-filled in the cylinder by the die casting machine punch, the mold is controlled by the oil temperature machine and the water temperature machine, the cooling water is cooled through the cold pipe at a water pressure of 0.6-1.0 MPa when the injection is performed, the high-pressure water in the pipe rapidly cools the local mold core; after the injection is completed, the mold is opened and the casting is ejected by the ejection system, and the cooling is formed;

[0028] 4) Demolding, the casting is taken out by the mechanical arm.

[0029] A baking method of a die-casting aluminum alloy with high electrical conductivity and high toughness, the die-casting aluminum alloy casting is heated to 220-240℃ at a heating rate of 150℃ / h, and after baking for 1-2h, it is air-cooled to room temperature, thereby obtaining a high-conductivity and high-toughness die-casting aluminum alloy.

[0030] Further supplement to the technical solution, the electrical conductivity of the die-casting aluminum alloy after baking is 30-32Ms / m, the tensile strength is ≥140MPa, the yield strength is ≥60MPa, and the elongation is ≥12%.

[0031] The beneficial effects are that (1) by specific rare earth modification, the alloy pressure casting property and electrical conductivity are improved; the affinity energy of rare earth La and Ce and aluminum element is large, Al 11 La3 and Al 11 Ce3 has a large crystallization latent heat, which is beneficial to the improvement of the flowability of the alloy; at the same time, compared with Si element in the die-casting aluminum alloy for improving flowability, the solid solubility of La and Ce in aluminum base is extremely low, close to zero, and it is extremely difficult to be solid-soluble in the aluminum base, which can reduce the lattice distortion to the maximum extent and has less effect on electrical conductivity than Si; in addition, rare earth has strong binding force with non-metallic elements such as H and O in the aluminum liquid, which can effectively remove hydrogen and oxygen, purify the aluminum liquid, and simultaneously react with Ti, V, Cr and other elements in the aluminum liquid to make the impurity elements change from solid solution state to precipitation state, thereby improving the electrical conductivity of the alloy;

[0032] (2) The morphology of Fe phase is modified by rare earth La, Ce and Ni instead of Mn, Fe in Al is easy to generate needle-like Al3Fe and β-AlFeSi phase, which seriously deteriorates the mechanical properties of the material and increases the scattering of electrons to reduce the electrical conductivity; currently, the addition of Mn can modify the Fe phase to reduce the influence of Fe, but the solid solution of Mn will seriously deteriorate the electrical conductivity of the material, and the present application modifies the Fe phase by rare earth and Ni to change the needle-like Fe phase into round CeFe2Al 10 and LaFe2Al10, FeNiAl9 and other ternary compounds, instead of the traditional method of modifying Fe phase by Mn element, which significantly improves the toughness of the material without losing electrical conductivity;

[0033] (3) Ni, Zr and Cu improve the mechanical properties of the material, the solid solubility of Ni and Zr in the aluminum matrix is low, and the existing form is mainly Al3Zr and Al3Ni sub-micron precipitates, the precipitates are stable in nature, can effectively pin the movement of dislocations, stabilize the microstructure, and ensure that the alloy has good reliability when serving at room temperature and high temperature environment; at the same time, by adding a small amount of Cu element, the Cu phase is aged to form a high-temperature stable phase θ-Al2Cu, and the addition of Si and Mg can form Mg2Si aging phase during the baking process, which can significantly improve the mechanical properties of the material, and with the precipitation of the precipitates, the solid solubility of Cu, Si and Mg in the aluminum matrix is significantly reduced, the lattice distortion is reduced, and the influence on the electrical conductivity is reduced while the mechanical properties are improved; and during the heat treatment process, the heat treatment temperature reaches the recovery temperature point of the alloy, and the point defects can migrate and neutralize, reducing the adverse effects of point defects on electrical conductivity, thereby reducing the adverse effects of supersaturated vacancies caused by the die casting process on electrical conductivity, so that the material has high electrical conductivity and high strength and toughness, in addition, the total amount of Mn, Cr, V and Ti is strictly controlled, and the impurity elements are reduced to reduce the electrical conductivity of the alloy;

[0034] (4) The fine-grained alloy preparation method combining rapid cooling with ball milling can significantly improve the fine-grained degree of the alloy, reduce the size of the alloy phase particles, and the sub-micron fine-grained alloy powder particles can be quickly and uniformly dissolved in the aluminum liquid, avoiding the inclusion and large particle phase caused by the addition of intermediate alloy, significantly reducing the inclusion and gas content in the aluminum liquid, improving the quality of the aluminum liquid, and being beneficial to the improvement of electrical conductivity and mechanical properties. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Microstructure diagram of Fe phase transformation of die-cast aluminum alloy;

[0036] Figure 2 Microstructure diagram of Cu Mg Si in solid solution state of die-cast aluminum alloy;

[0037] Figure 3 Microstructure diagram of Cu Mg Si in aging state of die-cast aluminum alloy; DETAILED DESCRIPTION

[0038] In order to make the technical personnel in the art more clearly understand the technical scheme, the technical scheme of the present application will be described in detail below:

[0039] A die-casting aluminum alloy with high conductivity and high toughness, which is composed of the following raw materials in percentage by weight: Fe:≤0.3wt%, Si:0.1-0.4wt%, Ce:≤1.5wt%, La:≤0.5wt%, Ni:≤4.0wt%, Zr:0.05-0.3wt%, B:0.05-0.15wt%, Mg:0.05-0.4wt%, Cu≤0.2wt%, Mn+Cr+Ti+V≤0.1wt%, the balance being Al and unavoidable impurities, and the sum of the weight percentages of the impurities being controlled to be below 0.1wt%.

[0040] The Zr and La, Ce are added in the form of fine-grained alloy, which is prepared by processing Al-Zr, Al-La and Al-Ce through high-speed gas quenching combined with planetary high-energy mechanical ball milling, to obtain fine-grained alloy powder, and the high-speed gas quenching combined with planetary high-energy mechanical ball milling comprises the following working steps:

[0041] Step one: adding Al-Zr, Al-La and Al-Ce intermetallic alloy respectively, specifically, the mass distribution is matched according to the component requirements to obtain the preset component intermetallic alloy;

[0042] Step two: heating the preset component intermetallic alloy to a molten state of 950-1200℃ through an induction heater;

[0043] Step three: forming small droplets by high-speed inert gas flow impact on the molten stream, and collecting the mixed fine-grained alloy powder after rapid cooling;

[0044] Step four: placing the mixed fine-grained alloy powder in a planetary high-energy ball mill under inert gas atmosphere protection for intermittent ball milling to promote further transformation of the alloy, and finally obtaining the required fine-grained alloy.

[0045] In the high-speed gas quenching method, the gas flow is helium, and the gas flow pressure is 3-8Mpa; in the high-energy mechanical ball milling method, the ball milling time is 20-60h, the ratio of running time to stopping time is 5:1, and the ball milling speed is 300-500r / min.

[0046] A die-casting aluminum alloy with high conductivity and high toughness, which is composed of the following raw materials in percentage by weight: Fe:≤0.3wt%, Si:0.1-0.4wt%, Ce:≤1.5wt%, La:≤0.5wt%, Ni:≤4.0wt%, Zr:0.05-0.3wt%, B:0.05-0.15wt%, Mg:0.05-0.4wt%, Cu≤0.2wt%, Mn+Cr+Ti+V≤0.1wt%, the balance being Al and unavoidable impurities, and the sum of the weight percentages of the impurities being controlled to be below 0.1wt%.

[0047] 1) According to the alloy component ratio, first put high-purity aluminum elements into a heating furnace, heat to 690℃, completely melt and keep for 15min;

[0048] 2) Heat to 760℃, add Si, Cu elemental and Al-Fe alloy;

[0049] 3) cooling to 730℃, adding Al-B, Al-Ni intermediate alloy and Al-Zr-La-Ce fine-grain alloy;

[0050] 4) cooling to 720℃, adding pure Mg metal material;

[0051] 5) after the raw materials are completely melted, the melt is refined and degassed, and finally cast to obtain aluminum alloy ingot.

[0052] Further supplement to the technical solution, the aluminum alloy casting is subjected to high-pressure die casting forming, and the high-pressure die casting forming working steps are as follows:

[0053] 1) melting the aluminum alloy ingot at 740℃ again and keeping the temperature;

[0054] 2) during the temperature keeping, protective gas is introduced and air is isolated, and then the die casting mold is injected;

[0055] 3) the molten alloy obtained in step 1) is pre-filled in the barrel by the punch of the die casting machine, the mold temperature is controlled by the oil temperature machine and the water temperature machine, and the cooling water passes through the cold pipeline at a water pressure of 0.6-1.0 MPa during the injection, the high-pressure water in the pipeline rapidly cools the local mold core; after the injection is completed, the mold is kept for 7-9 seconds, the mold is opened, and the casting is ejected by the ejection system, and is cooled and formed;

[0056] 4) demolding, and taking out the casting by the mechanical arm.

[0057] A baking method of a die-casting aluminum alloy with high electrical conductivity and high toughness, the die-casting aluminum alloy casting is heated to 220-240℃ at a heating rate of 150℃ / h, and after baking for 1-2h, it is air-cooled to room temperature, thereby obtaining a die-casting aluminum alloy with high electrical conductivity and high toughness, wherein the electrical conductivity of the die-casting aluminum alloy after baking is 30-32Ms / m, the tensile strength is ≥140MPa, the yield strength is ≥60MPa, and the elongation is ≥12%.

[0058] The die-casting aluminum alloys of examples 1-6 are prepared according to the above preparation method, and the prepared aluminum alloy is subjected to performance test, and the mechanical property analysis sample meets the mechanical property requirements of ASTM E8, and the conductivity analysis sample meets GB / T12966-2008 for sample preparation and determination.

[0059] Table 1 shows the content of each element in the aluminum alloy of examples 1-6

[0060]

[0061] Table 2 shows the performance of examples 1-6

[0062]

[0063]

[0064] The above technical solutions only reflect the preferred technical solutions of the present application, and some changes made by the skilled in the art to some parts thereof also reflect the principles of the present application and are within the scope of protection of the present application.

Claims

1. A die-cast aluminum alloy with high electrical conductivity and high strength and toughness, characterized in that, The alloy is composed of the following raw materials in percentage by weight: Fe: 0.1-0.3wt%, Si: 0.1-0.4wt%, Ce: 0.01-1.5wt%, La: 0.01-0.5wt%, Ni: 0.01-4.0wt%, Zr: 0.05-0.3wt%, B: 0.05-0.15wt%, Mg: 0.05-0.4wt%, Cu: 0.05-0.2wt%, Mn+Cr+Ti+V≤0.1wt%, and the balance of Al and inevitable impurities, with the total percentage by weight of the impurities controlled below 0.1wt%; The preparation method comprises the following steps: 1) preparing raw materials according to the alloy composition ratio, first putting high-purity aluminum elements into a heating furnace, heating to 690℃, completely melting and keeping for 15min; 2) heating to 760℃, adding Si, Cu elemental substances and Al-Fe alloy; 3) cooling to 730℃, adding Al-B, Al-Ni intermediate alloy and Al-Zr-La-Ce fine-grained alloy; 4) cooling to 720℃, adding pure Mg metal material; 5) after the raw materials are completely melted, the melt is refined and degassed, and finally an aluminum alloy ingot is obtained by casting, and the aluminum alloy ingot is subjected to high-pressure die casting; The high-pressure die casting working steps are as follows: 1) melting the aluminum alloy ingot at 740℃ again and keeping; 2) when keeping, protective gas is introduced to isolate from air, and then the die casting mold is injected; 3) the molten alloy obtained in step 1) is pre-filled in the barrel through the punch of the die casting machine, the mold temperature is controlled by an oil temperature machine and a water temperature machine, and when the die is injected, the cooling water passes through the cold pipeline at a water pressure of 0.6-1.0MPa, the pipeline high-pressure water rapidly cools the local mold core; after the injection is completed, the mold is opened, the ejection system ejects the casting, and the cooling is formed; 4) demolding, taking out the casting through a mechanical arm.

2. The die casting aluminium alloy with high electrical conductivity and high toughness according to claim 1, characterized in that, The Zr and La, Ce are added in the form of fine-grained alloy.

3. The die casting aluminium alloy with high electrical conductivity and high toughness according to claim 2, characterized in that, The fine-grained alloy is prepared by high-speed gas rapid cooling method combined with planetary high-energy mechanical ball milling method to treat Al-Zr, Al-La and Al-Ce.

4. The die casting aluminium alloy with high electrical conductivity and high toughness according to claim 3, characterized in that, The high-speed gas rapid cooling method combined with planetary high-energy mechanical ball milling method comprises the following working steps: Step one: adding Al-Zr, Al-La and Al-Ce intermediate phase alloy respectively, specifically, the mass distribution form is matched according to the component requirements to obtain the preset component intermediate alloy; Step two: heating the preset component intermediate alloy to 950-1200℃ molten state by an induction heater; Step three: forming small droplets by high-speed inert gas flow impact on the molten stream, collecting the mixed fine-grained alloy powder after rapid cooling; Step four: placing the mixed fine-grained alloy powder in a planetary high-energy ball mill under inert gas atmosphere protection for intermittent ball milling to promote further transformation of the alloy, and finally obtaining the required fine-grained alloy.

5. The die casting aluminium alloy with high electrical conductivity and high toughness according to claim 4, characterized in that, The gas flow in the high-speed gas quenching method is helium, and the gas flow pressure is 3-8 MPa; the ball milling time in the high-energy mechanical ball milling method is 20-60 h, the ratio of running time to stopping time is 5:1, and the ball milling speed is 300-500 r / min.

6. A method of baking the die-cast aluminum alloy having high electric conductivity and high toughness according to claim 1, characterized by, The high-conductivity and high-strength die-casting aluminum alloy is obtained by heating the die-casting aluminum alloy casting to 220-240℃ at a heating rate of 150℃ / h, air cooling to room temperature after baking for 1-2 h.

7. The method of baking a die casting aluminum alloy having high electrical conductivity and high strength and toughness according to claim 6, characterized in that, The electrical conductivity of the die-casting aluminum alloy after baking is 30-32 Ms / m, the tensile strength is ≥140 MPa, the yield strength is ≥60 MPa, and the elongation is ≥12%. The electrical conductivity of the die-casting aluminum alloy after baking is 30-32 Ms / m, the tensile strength is ≥140 MPa, the yield strength is ≥60 MPa, and the elongation is ≥12%.

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