Semi-solid die-casting high-strength and high-toughness aluminum alloy and preparation method thereof

Abstract

The invention discloses a semi-solid die-casting high-strength and high-toughness aluminum alloy and a preparation method thereof. The semi-solid die-casting high-strength and high-toughness aluminum alloy comprises the following components in percentage by mass: 6.0 to 8.0 percent of Si, 0.1 to 0.3 percent of Cu, 0.25 to 0.35 percent of Mn, 0.2 to 0.5 percent of Mg, 0.01 to 0.1 percent of Cr, 0.002 to 0.02 percent of Ti, 0.01 to 0.03 percent of Sb, 20 to 90 ppm of rare earth elements and the balance of Al and inevitable impurities. The semi-solid die-casting high-strength and high-toughness aluminum alloy has good mechanical property and casting property, the tensile strength of the semi-solid die-casting high-strength and high-toughness aluminum alloy is not lower than 360 MPa, the yield strength is not lower than 280 MPa, and the ductility is not lower than 7%. According to the method, a special semi-solid die-casting forming process is adopted, various complex parts can be formed, the mechanical property of a casting is improved, meanwhile, the defects of the casting are reduced, the yield is increased, and therefore the high-strength and high-toughness aluminum alloy with high strength, good plasticity and excellent semi-solid die-casting process performance is prepared.

Description

TECHNICAL FIELD

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

[0002] From the aspects of light weight, low cost, environmental protection and the like, the aluminum alloy is one of the first choices for light weight of the automobile manufacturing industry, and development of the aluminum alloy for automobiles has a positive effect on improving the international competitiveness of the automobile industry of China. The aluminum alloy for automobiles is mainly divided into deformed aluminum alloy and cast aluminum alloy, wherein forged aluminum parts account for 1%-3%, cast aluminum parts account for about 80%, and the rest are processed profiles, and in the cast aluminum alloy for automobiles, the die-casting parts account for as high as 80%. However, in the traditional die-casting process, the liquid metal has a high filling speed, and the liquid is prone to form a turbulent flow in the mold cavity, and air in the mold cavity is rolled into the product; the liquid meets the mold at a moment, and the temperature difference is large, the surface liquid rapidly solidifies, and the flow resistance of the liquid in the core is increased, so the liquid cannot be well fused and cold shut is formed, and in addition, the alloy introduces oxides or some other impurities in the smelting and casting processes, and finally the performance of the product is reduced.

[0003] With the rapid development of new energy vehicles and the increasing requirement for light weight, the demand for the die-casting aluminum alloy with high strength and high toughness is increased, however, the traditional Al-Si series die-casting aluminum alloy only has moderate strength, and the plasticity and toughness are low, and it is difficult to meet the requirements of the automobile aluminum alloy.

[0004] Therefore, it is urgent to develop an aluminum alloy casting to solve the problems of insufficient strength and low toughness of the existing aluminum alloy casting, so as to meet the requirements of the automobile aluminum alloy. SUMMARY

[0005] In view of the problems in the prior art, the application discloses a semi-solid die-casting high-strength and high-toughness aluminum alloy and a preparation method thereof, and the main purpose is to provide a semi-solid die-casting high-strength and high-toughness aluminum alloy, which has high strength and high plasticity, and can meet the requirements of the high-strength and high-toughness automobile aluminum alloy.

[0006] In order to achieve the above-mentioned application purposes, the application provides the following technical scheme:

[0007] The application provides a semi-solid die-casting high-strength and high-toughness aluminum alloy, the high-strength and high-toughness aluminum alloy comprises the following components in percentage by mass: Si: 6.0-8.0%, Cu: 0.1-0.3%, Mn: 0.25-0.35%, Mg: 0.2-0.5%, Cr: 0.01-0.1%, Ti: 0.002-0.02%, Sb: 0.01-0.03%, rare earth elements: 20-90ppm, and the balance is Al and inevitable impurities.

[0008] Further, the high-strength and high-toughness aluminum alloy comprises the following components in percentage by mass: Si: 6.0-7.5%, Cu: 0.15-0.25%, Mn: 0.25-0.3%, Mg: 0.2-0.4%, Cr: 0.05-0.08%, Ti: 0.005-0.01%, Sb: 0.01-0.02%, and rare earth elements: 40-60ppm.

[0009] Further, the high-strength and high-toughness aluminum alloy comprises the following components in percentage by mass: Si: 6.5%, Cu: 0.2%, Mn: 0.27%, Mg: 0.3%, Cr: 0.07%, Ti: 0.007%, Sb: 0.015%, and rare earth elements: 50ppm.

[0010] Further, the rare earth elements are Ce and / or Y.

[0011] The application provides a preparation method of a semi-solid die-casting high-strength and high-toughness aluminum alloy, comprising the following steps:

[0012] (1) Drying of raw materials: according to the component percentage by mass of the aluminum alloy, the formula amount of aluminum ingot (purity ≥ 99.9wt%), silicon ingot (purity ≥ 99.9wt%), magnesium ingot (purity ≥ 99.95wt%), Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are weighed, wherein the aluminum ingot, fast-acting silicon, and magnesium ingot are dried at 90-110℃, and the Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are dried at 140-160℃;

[0013] (2) Melting and modification: the inner wall of a crucible is coated with a slag remover, and the crucible is preheated to 260-300℃, the aluminum ingot is first melted at 760-800℃, then the silicon ingot, magnesium ingot, Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and the slag remover are added and heated to melt, after the alloy is completely melted, the temperature of the melt is lowered to 690-710℃, then the Al-Re intermediate alloy is added for modification treatment, and the aluminum alloy melt is obtained after uniform stirring;

[0014] (3) Refining: the aluminum alloy melt in step (2) is heated, then the refining agent is pressed into the aluminum alloy melt at about 1 / 2 below the melt surface in batches by a bell, and uniform and slow clockwise rotation is performed, and the refining time is 10-15min;

[0015] (4) deslagging: after the refining is completed, the bell is taken out, the residual oxide is cleaned, and the inclusions on the surface of the aluminum alloy melt are fished out with a deslagging ladle;

[0016] (5) aluminum alloy solution semi-solidification: the aluminum alloy melt after deslagging is kept at 630-650℃ for 5-10min, and then is prepared into aluminum alloy semi-solid slurry by stirring and vibration method;

[0017] (6) die casting: the aluminum alloy semi-solid slurry obtained in step (5) is die cast to obtain semi-solid die cast aluminum alloy;

[0018] (7) solution heat treatment: the semi-solid die cast aluminum alloy obtained in step (6) is solution treated at 570-590℃ for 8-10h, water quenched, aged at 210-230℃ for 4-6h, and then cooled in the furnace to obtain semi-solid die cast high-strength and high-toughness aluminum alloy.

[0019] Further, the deslagging agent in step (2) comprises sodium fluoride, potassium chloride and magnesium chloride, the mass ratio of the sodium fluoride, potassium chloride and magnesium chloride is 1:1:1, and the addition amount of the deslagging agent is 0.1-0.3% of the aluminum alloy melt.

[0020] Further, the refining agent in step (3) is FF102 refining agent, and the aluminum alloy melt is heated to 730-740℃.

[0021] Further, the stirring and vibration method in step (5) is ultrasonic vibration under the stirring of a graphite rotor, wherein the rotating speed of the graphite rotor is 300-400rpm, the ultrasonic vibration frequency is 60-80Hz, and the ultrasonic vibration time is 15-25s.

[0022] Further, the die casting temperature in step (6) is 200-300℃, the injection speed is 0.1-1m / s, the injection specific pressure is 30-50MPa, the pressurization pressure is 60-80MPa, and the pressure maintaining time is 5-10s.

[0023] Through the above technical scheme, the semi-solid die cast high-strength and high-toughness aluminum alloy of the application can play a good gas and inclusion purifying effect and grain refining modification effect on the alloy melt by selecting appropriate alloying elements and adjusting and optimizing the formula, and can increase the melt fluidity and improve the casting performance by cooperation of Cu, Mn, Mg, Cr, Ti, Sb and rare earth elements;

[0024] In addition, the application adopts a special semi-solid die casting forming process, which can form various complex parts, improves the mechanical properties of the castings, reduces the casting defects, and improves the yield, so that a high-strength and high-toughness aluminum alloy with high strength, good plasticity and excellent semi-solid die casting process performance is prepared. DETAILED DESCRIPTION

[0025] The specific embodiments of the present application are further described below with reference to the following examples, which are merely illustrative of the present application and are not to be taken in a limiting sense.

[0026] The present application provides a semi-solid die casting high-strength and high-toughness aluminum alloy, which contains alloying elements, inevitable impurities and the balance of aluminum elements; the semi-solid aluminum alloy contains the following components in percentage by mass: Si: 6.0-8.0%, Cu: 0.1-0.3%, Mn: 0.25-0.35%, Mg: 0.2-0.5%, Cr: 0.01-0.1%, Ti: 0.002-0.02%, Sb: 0.01-0.03%, rare earth elements: 20-90ppm, the balance being Al and inevitable impurities. Among them, ppm is one ten-thousandth, that is, 1% = 10000ppm.

[0027] The present application can play a good degassing and impurity removal purification effect and grain refinement modification effect on the alloy melt by selecting suitable alloying elements and adjusting and optimizing the formula, and can increase the melt fluidity and improve the casting performance. According to the semi-solid die casting aluminum alloy of the present application, when the composition of the semi-solid die casting aluminum alloy is within the above range, good casting performance can be obtained at the same time, and high mechanical performance can be obtained. The semi-solid die casting aluminum alloy obtained by using the formula has a tensile strength of not less than 360MPa, a yield strength of not less than 280MPa, and an elongation of not less than 7%.

[0028] The effects and contents of the above-mentioned components are described as follows:

[0029] Si can form Al+Si eutectic liquid phase with Al in the aluminum alloy, improve the die casting fluidity of the aluminum alloy, and also improve the strength and machining performance of the aluminum alloy. The higher the content of Si, the more eutectic liquid phase, and the better the die casting fluidity of the aluminum alloy, but the plasticity of the die casting aluminum alloy will decrease. When the content of Si is less than 6.0%, the fluidity of the aluminum alloy cannot meet the process requirements of semi-solid die casting, and when the content of Si exceeds 8.0%, the plasticity of the aluminum alloy will decrease significantly. In order to ensure that the aluminum alloy has sufficient semi-solid die casting fluidity and plasticity, therefore, the content of Si is selected to be 6.0-8.0%.

[0030] Cu element in semi-solid die casting aluminum alloy has solid solution strengthening effect, and CuAl2 strengthening phase is precipitated during aging heat treatment of aluminum alloy, which enhances the strength of aluminum alloy. When Cu content is lower than 0.1%, copper has certain solid solution strengthening and aging strengthening effect in aluminum alloy, and too low content of copper may significantly reduce the mechanical properties of the alloy, and insufficient copper content will reduce the fluidity of the aluminum alloy, affect the filling performance in the casting process, and may cause defects in the castings. When Cu content is higher than 0.3%, excessive copper will exist in the form of micron-sized Al2Cu phase, and the brittleness and debonding of these phases from the matrix will easily become a fracture source, causing crack initiation and propagation and leading to alloy fracture, and in the casting process, high copper content aluminum alloy is prone to crack at high temperature, affecting the quality of the castings. Therefore, the Cu content is selected to be 0.1-0.3%.

[0031] The content of Mn is controlled to be 0.25-0.35%, and the addition of Mn in the above range is beneficial to prevent the recrystallization process of the aluminum alloy, increase the recrystallization temperature, and also can significantly refine the recrystallized grains. At the same time, the addition of Mn is also beneficial to dissolve impurity iron to form (Fe, Mn) Al6, and reduce the harmful effect of iron. Excessive addition will reduce the toughness of the material.

[0032] Mg element in semi-solid die casting aluminum alloy can form Mg2Si strengthening phase with Si, which enhances the strength of semi-solid die casting aluminum alloy. If the content of magnesium is higher than 0.5%, excessive magnesium content will cause excessive β phase (Mg2Al3) to form in the aluminum alloy, which will reduce the strength and toughness of the alloy, and excessive magnesium will make the alloy brittle, reduce its ductility, and increase the risk of fracture during processing and use. If the content of magnesium is lower than 0.2%, too low magnesium content will result in insufficient strength and hardness of the alloy, which cannot meet the requirements of high-strength aluminum alloy suspension bracket.

[0033] The content of Cr is controlled to be 0.01-0.1%, and when the content of Cr is higher than 0.1%, hard and brittle intermetallic compounds will be formed in the aluminum alloy, which will reduce the ductility and impact toughness of the alloy, and excessive Cr content will increase the quenching sensitivity of the alloy, making the aluminum alloy more prone to crack during heat treatment. If the content of Cr is lower than 0.01%, the grain of the alloy will be coarsened, which will reduce the strength and hardness of the alloy, therefore, the content of Cr is selected to be 0.01-0.1%.

[0034] Ti mainly plays a role of refining α-Al grains in the semi-solid die-casting aluminum alloy, improves the uniformity of the structure and composition of the aluminum alloy, and improves the fluidity, strength and plasticity of the semi-solid die-casting aluminum alloy. When the content of Ti is less than 0.002%, the grain refinement effect is not obvious. The higher the content of Ti is, the better the grain refinement effect is, but when the content of Ti exceeds 0.02%, the performance of the aluminum alloy will be significantly reduced. Therefore, the content of Ti is selected to be 0.002%-0.02%.

[0035] Sb mainly plays a role of refining eutectic Si phase in the semi-solid die-casting aluminum alloy, can change the morphology of eutectic Si in the semi-solid die-casting aluminum alloy from slender needle shape to fine and uniform granular shape, significantly improves the strength and plasticity of the semi-solid die-casting aluminum alloy, and the content of Sb is selected to be 0.01%-0.03%.

[0036] Rare earth element Re can significantly refine grains and improve the mechanical properties of the alloy. The content of the rare earth element Re is controlled to be 20-90ppm. When the content of the rare earth element exceeds 90ppm, the grain refinement effect may be reduced, even the phenomenon of grain coarsening occurs, which leads to the performance of the alloy to be reduced. If the content of the rare earth element is less than 20ppm, the expected grain refinement effect may not be achieved, which further affects the mechanical properties of the alloy.

[0037] The application will be further described through examples.

[0038] Example 1

[0039] The semi-solid die-casting high-strength and high-toughness aluminum alloy of the example comprises the following components in percentage by mass: Si: 6.5%, Cu: 0.2%, Mn: 0.27%, Mg: 0.3%, Cr: 0.07%, Ti: 0.007%, Sb: 0.015%, and rare earth element: 50ppm.

[0040] The preparation method of the semi-solid die-casting high-strength and high-toughness aluminum alloy comprises the following steps:

[0041] (1) Drying of raw materials: according to the percentage by mass of the components of the aluminum alloy, the formula amount of aluminum ingot (purity ≥99.9wt%), silicon ingot (purity ≥99.9wt%), magnesium ingot (purity ≥99.95wt%), Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy and Al-Re intermediate alloy are weighed according to Table 1, wherein the aluminum ingot, quick-dissolving silicon and magnesium ingot are dried at 100°C, and the Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy and Al-Re intermediate alloy are dried at 150°C;

[0042] (2) melting modification: the inner wall of the crucible is coated with a slag remover, and the crucible is preheated to 280℃, the aluminum ingot is first melted at 780℃, then the silicon ingot, the magnesium ingot, the Al-Cu intermediate alloy, the Al-Mn intermediate alloy, the Al-Cr intermediate alloy, the Al-Ti intermediate alloy, the Al-Sb intermediate alloy and the slag remover are added and heated to melt, after the alloy is completely melted, the melt temperature is lowered to 700℃, and the Al-Re intermediate alloy is added for modification treatment, and the aluminum alloy melt is obtained after uniform stirring;

[0043] (3) refining: the aluminum alloy melt in step (2) is heated, then FF102 refining agent is pressed into the aluminum alloy melt under the melt surface about 1 / 2 by the bell cover, and uniform and slow clockwise rotation is performed, and the refining time is 13 min;

[0044] (4) slag removal: after the refining is completed, the bell cover is removed, the residual oxides are cleaned, and the inclusions on the surface of the aluminum alloy melt are removed with a slag spoon;

[0045] (5) semi-solidification of aluminum alloy solution: the aluminum alloy melt after slag removal is kept at 640℃ for 7 min, then ultrasonic vibration is performed under the stirring of a graphite rotor, wherein the rotation speed of the graphite rotor is 350 rpm, the ultrasonic vibration frequency is 70 Hz, and the ultrasonic vibration time is 20 s, to prepare an aluminum alloy semi-solid slurry;

[0046] (6) die casting: the aluminum alloy semi-solid slurry obtained in step (5) is die cast, the die casting temperature is 250℃, the injection speed is 0.5 m / s, the injection specific pressure is 40 MPa, the boost pressure is 70 MPa, and the holding time is 70 s, to obtain a semi-solid die cast aluminum alloy;

[0047] (7) solid solution heat treatment: the semi-solid die cast aluminum alloy obtained in step (6) is subjected to solid solution treatment at 580℃ for 9 h, water quenching, and then is subjected to aging treatment at 220℃ for 5 h, and then is cooled in the furnace to obtain a semi-solid die cast high-strength high-toughness aluminum alloy.

[0048] Example 2

[0049] The semi-solid die cast high-strength high-toughness aluminum alloy of the present embodiment comprises the following components by mass percentage: Si: 6.0%, Cu: 0.1%, Mn: 0.25%, Mg: 0.2%, Cr: 0.01%, Ti: 0.002%, Sb: 0.01%, and rare earth elements: 20 ppm.

[0050] The preparation method of the semi-solid die cast high-strength high-toughness aluminum alloy comprises the following steps:

[0051] (1)Material drying: according to the mass percentage of the aluminum alloy composition, the formula amount of aluminum ingot (purity ≥ 99.9wt%), silicon ingot (purity ≥ 99.9wt%), magnesium ingot (purity ≥ 99.95wt%), Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are weighed, wherein the aluminum ingot, fast-acting silicon, and magnesium ingot are dried at 110°C, and the Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are dried at 140°C;

[0052] (2) Melting and modification: the inner wall of the crucible is coated with a slag remover, and the crucible is preheated to 290°C. First, melt the aluminum ingot at 790°C, then add the silicon ingot, magnesium ingot, Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and add the slag remover and heat to melt. After the alloy is completely melted, the melt temperature is lowered to 710°C, and then Al-Re intermediate alloy is added for modification treatment. Stir uniformly to obtain the aluminum alloy melt;

[0053] (3) Refining: the aluminum alloy melt in step (2) is heated, then the refining agent is pressed into the aluminum alloy melt about 1 / 2 below the melt surface in batches using a bell cover, and uniform and slow clockwise rotation is performed for 14 minutes.

[0054] (4) Slag removal: after refining is completed, the bell cover is removed, the remaining oxides are cleaned, and the inclusions on the surface of the aluminum alloy melt are removed with a slag spoon;

[0055] (5) Aluminum alloy solution semi-solidification: the aluminum alloy melt after slag removal is kept at 650°C for 5 minutes, and then prepared into an aluminum alloy semi-solid slurry by stirring and vibration method;

[0056] (6) Die casting: the aluminum alloy semi-solid slurry obtained in step (5) is die cast to obtain a semi-solid die cast aluminum alloy;

[0057] (7) Solution heat treatment: the semi-solid die cast aluminum alloy obtained in step (6) is solution treated at 590°C for 8h, water quenched, aged at 210°C for 6h, and then cooled in the furnace to obtain a semi-solid die cast high-strength high-toughness aluminum alloy.

[0058] The slag remover in step (2) includes sodium fluoride, potassium chloride, and magnesium chloride, and the mass ratio of the sodium fluoride, potassium chloride, and magnesium chloride is 1:1:1. The addition amount of the slag remover is 0.3% of the aluminum alloy melt.

[0059] The refining agent in step (3) is FF102 refining agent, and the aluminum alloy melt is heated to 730-740℃.

[0060] The stirring and vibration method in step (5) is ultrasonic vibration under the stirring of a graphite rotor, wherein the rotating speed of the graphite rotor is 400 rpm, the ultrasonic vibration frequency is 60 Hz, and the ultrasonic vibration time is 25 s.

[0061] The die casting temperature in step (6) is 200℃, the injection speed is 0.8 m / s, the injection specific pressure is 50 MPa, the boost pressure is 60 MPa, and the holding time is 10 s.

[0062] Example 3

[0063] The semi-solid die-cast high-strength and high-toughness aluminum alloy of the embodiment comprises the following components in percentage by mass: Si: 7.5%, Cu: 0.3%, Mn: 0.3%, Mg: 0.5%, Cr: 0.1%, Ti: 0.01%, Sb: 0.027%, and rare earth elements: 90 ppm.

[0064] The preparation method of the semi-solid die-cast high-strength and high-toughness aluminum alloy comprises the following steps:

[0065] (1) Drying of raw materials: according to the percentage by mass of the components of the aluminum alloy, the formula amount of aluminum ingots (purity ≥ 99.9wt%), silicon ingots (purity ≥ 99.9wt%), magnesium ingots (purity ≥ 99.95wt%), Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are weighed, wherein the aluminum ingots, fast-dissolving silicon, and magnesium ingots are dried at 110℃, and the Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are dried at 160℃;

[0066] (2) Melting and modification: the inner wall of the crucible is coated with a slag remover, and the crucible is preheated to 300℃. The aluminum ingots are first melted at 800℃, then the silicon ingots, magnesium ingots, Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and slag remover are added and heated to melt. After the alloy is completely melted, the melt temperature is lowered to 710℃, and the Al-Re intermediate alloy is added for modification treatment. The mixture is stirred uniformly to obtain the aluminum alloy melt;

[0067] (3) Refining: the aluminum alloy melt in step (2) is heated, then the refining agent is pressed into the aluminum alloy melt about 1 / 2 below the melt surface in batches by a bell jar, and uniform and slow clockwise rotation is performed, and the refining time is 15 min;

[0068] (4) Deslagging: After refining is completed, the bell is removed, and the residual oxides are cleaned away, and the inclusions on the surface of the aluminum alloy melt are scooped out with a deslagging spoon;

[0069] (5) Semi-solidification of the aluminum alloy solution: the aluminum alloy melt after deslagging is kept at 650°C for 10 min, and then is prepared into an aluminum alloy semi-solid slurry by a stirring vibration method;

[0070] (6) Die casting: the aluminum alloy semi-solid slurry obtained in step (5) is die cast to obtain a semi-solid die cast aluminum alloy;

[0071] (7) Solution heat treatment: the semi-solid die cast aluminum alloy obtained in step (6) is solution treated at 590°C for 10 h, and after water quenching, is aged at 230°C for 6 h, and after furnace cooling, a semi-solid die cast high-strength high-toughness aluminum alloy is obtained.

[0072] The deslagging agent in step (2) comprises sodium fluoride, potassium chloride and magnesium chloride, the mass ratio of the sodium fluoride, the potassium chloride and the magnesium chloride is 1:1:1, and the addition amount of the deslagging agent is 0.3% of the aluminum alloy melt.

[0073] The refining agent in step (3) is selected to be FF102 refining agent, and the aluminum alloy melt is heated to 740°C.

[0074] The stirring vibration method in step (5) is ultrasonic vibration under the stirring of a graphite rotor, wherein the rotating speed of the graphite rotor is 400 rpm, the ultrasonic vibration frequency is 80 Hz, and the ultrasonic vibration time is 25 s.

[0075] The die casting temperature in step (6) is 300°C, the injection speed is 1 m / s, the injection specific pressure is 50 MPa, the boost pressure is 80 MPa, and the pressure maintaining time is 10 s.

[0076] Example 4

[0077] The semi-solid die cast high-strength high-toughness aluminum alloy of the embodiment comprises the following components in percentage by mass: Si: 8.0%, Cu: 0.2%, Mn: 0.35%, Mg: 0.35%, Cr: 0.05%, Ti: 0.02%, Sb: 0.03%, and rare earth elements: 40 ppm.

[0078] The preparation method of the semi-solid die cast high-strength high-toughness aluminum alloy comprises the following steps:

[0079] (1)Material drying: according to the aluminum alloy composition mass percentage, the formula amount of aluminum ingot (purity ≥ 99.9wt%), silicon ingot (purity ≥ 99.9wt%), magnesium ingot (purity ≥ 99.95wt%), Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, Al-Re intermediate alloy are weighed, wherein the aluminum ingot, fast-acting silicon, magnesium ingot are dried at 90℃, the Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy and Al-Re intermediate alloy are dried at 140℃;

[0080] (2)Melting and modification: the inner wall of the crucible is coated with slag remover, and the crucible is preheated to 260℃, the aluminum ingot is first melted at 760℃, then the silicon ingot, magnesium ingot, Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy are added, and the slag remover is added and heated to melt, after the alloy is completely melted, the melt temperature is lowered to 690℃, then Al-Re intermediate alloy is added for modification treatment, and the aluminum alloy melt is obtained after uniform stirring;

[0081] (3)Refining: the aluminum alloy melt in step (2) is heated, then the refining agent is pressed into the aluminum alloy melt under the melt surface about 1 / 2 by the bell cover, and uniform and slow clockwise rotation is performed, the refining time is 10 min;

[0082] (4)Slag removal: after the refining is completed, the bell cover is removed, the residual oxides are cleaned, and the inclusions on the surface of the aluminum alloy melt are fished out with a slag spoon;

[0083] (5)Aluminum alloy solution semi-solidification: the aluminum alloy melt after slag removal is kept at 630℃ for 5 min, and then prepared into aluminum alloy semi-solid slurry by stirring and vibration method;

[0084] (6)Die casting: the aluminum alloy semi-solid slurry obtained in step (5) is die cast to obtain semi-solid die cast aluminum alloy;

[0085] (7)Solution heat treatment: the semi-solid die cast aluminum alloy obtained in step (6) is solution treated at 570℃ for 8h, water quenched, aged at 210℃ for 4h, and then cooled in the furnace to obtain semi-solid die cast high-strength high-toughness aluminum alloy.

[0086] The slag remover in step (2) includes sodium fluoride, potassium chloride and magnesium chloride, the mass ratio of sodium fluoride, potassium chloride and magnesium chloride is 1:1:1, and the addition amount of the slag remover is 0.1% of the aluminum alloy melt.

[0087] The refining agent in step (3) is selected from FF102 refining agent, and the aluminum alloy melt is heated to 730℃.

[0088] The stirring vibration method in step (5) is ultrasonic vibration under stirring of a graphite rotor, wherein the rotation speed of the graphite rotor is 300 rpm, the ultrasonic vibration frequency is 60 Hz, and the ultrasonic vibration time is 15 s.

[0089] The die casting temperature in step (6) is 200℃, the injection speed is 0.1 m / s, the injection specific pressure is 30 MPa, the boost pressure is 60 MPa, and the holding time is 5 s.

[0090] Example 5

[0091] The semi-solid die-cast high-strength and high-toughness aluminum alloy of the embodiment comprises the following components in percentage by mass: Si: 6.5%, Cu: 0.15%, Mn: 0.3%, Mg: 0.25%, Cr: 0.09%, Ti: 0.005%, Sb: 0.01%, and rare earth elements: 70 ppm.

[0092] The preparation method of the semi-solid die-cast high-strength and high-toughness aluminum alloy comprises the following steps:

[0093] (1) Drying of raw materials: according to the percentage by mass of the components of the aluminum alloy, the formula amount of aluminum ingots (purity ≥ 99.9wt%), silicon ingots (purity ≥ 99.9wt%), magnesium ingots (purity ≥ 99.95wt%), Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are weighed, wherein the aluminum ingots, fast-dissolving silicon, and magnesium ingots are dried at 95℃, and the Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and Al-Re intermediate alloy are dried at 145℃;

[0094] (2) Melting and modification: the inner wall of the crucible is coated with a slag remover, and the crucible is preheated to 270℃. The aluminum ingots are first melted at 790℃, then the silicon ingots, magnesium ingots, Al-Cu intermediate alloy, Al-Mn intermediate alloy, Al-Cr intermediate alloy, Al-Ti intermediate alloy, Al-Sb intermediate alloy, and the slag remover are added and heated to melt. After the alloy is completely melted, the melt temperature is lowered to 700℃, and the Al-Re intermediate alloy is added for modification treatment. The aluminum alloy melt is obtained after uniform stirring;

[0095] (3) Refining: the aluminum alloy melt in step (2) is heated, then the refining agent is pressed into the aluminum alloy melt about 1 / 2 below the melt surface in batches using a bell cover, and uniform and slow clockwise rotation is performed. The refining time is 14 min.

[0096] (4) Deslagging: After the refining is completed, the bell is taken out, the residual oxides are cleaned, and the inclusions on the surface of the aluminum alloy melt are scooped out with a deslagging scoop;

[0097] (5) Semi-solidification of the aluminum alloy solution: the aluminum alloy melt after deslagging is kept at 640°C for 9 min, and then is prepared into an aluminum alloy semi-solid slurry by a stirring vibration method;

[0098] (6) Die casting: the aluminum alloy semi-solid slurry obtained in step (5) is die cast to obtain a semi-solid die cast aluminum alloy;

[0099] (7) Solution heat treatment: the semi-solid die cast aluminum alloy obtained in step (6) is solution treated at 585°C for 9.5 h, water quenched, aged at 220°C for 5.5 h, and then cooled in the furnace to obtain a semi-solid die cast high-strength high-toughness aluminum alloy.

[0100] The deslagging agent in step (2) comprises sodium fluoride, potassium chloride and magnesium chloride, the mass ratio of the sodium fluoride, the potassium chloride and the magnesium chloride is 1:1:1, and the addition amount of the deslagging agent is 0.1% of the aluminum alloy melt.

[0101] The refining agent in step (3) is FF102 refining agent, and the aluminum alloy melt is heated to 735°C.

[0102] The stirring vibration method in step (5) is ultrasonic vibration under the stirring of a graphite rotor, wherein the rotating speed of the graphite rotor is 350 rpm, the ultrasonic vibration frequency is 65 Hz, and the ultrasonic vibration time is 20 s.

[0103] The die casting temperature in step (6) is 280°C, the injection speed is 0.7 m / s, the injection specific pressure is 35 MPa, the boost pressure is 75 MPa, and the pressure holding time is 6 s.

[0104] Comparative Example 1

[0105] The comparative example adopts the method and raw materials of Example 1, except that no rare earth element is added.

[0106] Comparative Example 2

[0107] The comparative example adopts the method and raw materials of Example 1, except that the content of the rare earth element in the comparative example is 110 ppm.

[0108] Comparative Example 3

[0109] The comparative example adopts the method and raw materials of Example 1, except that no Sb element is added.

[0110] Comparative Example 4

[0111] The comparative example adopts the method and raw materials of Example 1, except that the content of Sb element in the comparative example is 0.04%.

[0112] Comparative Example 5

[0113] The comparative example adopts the method and raw materials of Example 1, except that no Ti element is added.

[0114] Comparative Example 6

[0115] The comparative example adopts the method and raw materials of Example 1, except that the content of Sb element in the comparative example is 0.03%.

[0116] Test Example

[0117] The aluminum alloy obtained in the above examples and comparative examples is subjected to the following performance tests:

[0118] Tensile strength: The tensile strength test is performed according to the method disclosed in the national standard GB / T 228.1-2010 Metallic Materials-Tensile Testing-Part 1: Method of Test at Room Temperature;

[0119] Yield strength: The yield strength test is performed according to the method disclosed in the national standard GB / T 228.1-2010 Metallic Materials-Tensile Testing-Part 1: Method of Test at Room Temperature;

[0120] Elongation after fracture: The elongation after fracture test is performed according to the method disclosed in the national standard GB / T 228.1-2010 Metallic Materials-Tensile Testing-Part 1: Method of Test at Room Temperature.

[0121] The above test results are summarized in Table 1.

[0122] Table 1: Test results of semi-solid die-casting high-strength and high-ductility aluminum alloy of examples and comparative examples

[0123]

[0124]

[0125] From the records and statistical data of Table 1, the semi-solid die-casting aluminum alloy prepared by the embodiment of the application has more excellent tensile strength, yield strength and elongation than the comparative examples. Specifically, the tensile strength of the semi-solid die-casting aluminum alloy of the embodiment is not less than 360 MPa, the yield strength is not less than 280 MPa, and the elongation is not less than 7.5%. In addition, as can be seen from the comparative examples, the addition of rare earth elements, Ti and Sb, and the excessive addition of the content will affect the tensile strength, yield strength and elongation of the prepared semi-solid die-casting aluminum alloy. Through comparison, it can be seen that the present application refines the Fe-rich phase by the composite addition of Cr and Sb elements, and refines the eutectic Si phase by the addition of Ti element. In addition, the addition of rare earth elements can promote the spheroidization of the alpha-Al grains, thereby providing the semi-solid die-casting aluminum alloy with strength, toughness and die-casting performance.

[0126] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A semi-solid die-cast high-strength and high-toughness aluminum alloy, characterized in that: It contains the following components in mass percentage: Si: 6.0-8.0%, Cu: 0.1-0.3%, Mn: 0.25-0.35%, Mg: 0.2-0.5%, Cr: 0.01-0.1%, Ti: 0.002-0.02%, Sb: 0.01-0.03%, rare earth elements: 20-90ppm, and the balance is Al and unavoidable impurities.

2. The semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 1, characterized in that: It contains the following components in mass percentage: Si: 6.0-7.5%, Cu: 0.15-0.25%, Mn: 0.25-0.3%, Mg: 0.2-0.4%, Cr: 0.05-0.08%, Ti: 0.005-0.01%, Sb: 0.01-0.02%, rare earth elements: 40-60 ppm.

3. The semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 1, characterized in that: The composition includes the following components in mass percentage: Si: 6.5%, Cu: 0.2%, Mn: 0.27%, Mg: 0.3%, Cr: 0.07%, Ti: 0.007%, Sb: 0.015%, and rare earth elements: 50 ppm.

4. The semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 1, characterized in that: The rare earth element is Ce and / or Y.

5. The method for preparing a semi-solid die-cast high-strength and high-toughness aluminum alloy according to any one of claims 1 to 4, characterized in that: The steps include: (1) Material preparation and drying: according to the mass percentage of the components of the aluminum alloy, weigh the formulated amount of aluminum ingots (purity ≥99.9wt%), silicon ingots (purity ≥99.9wt%), magnesium ingots (purity ≥99.95wt%), Al-Cu master alloys, Al-Mn master alloys, Al-Cr master alloys, Al-Ti master alloys, Al-Sb master alloys, and Al-Re master alloys, wherein the aluminum ingots, instant silicon, and magnesium ingots are dried at 90-110° C., and the Al-Cu master alloys, Al-Mn master alloys, Al-Cr master alloys, Al-Ti master alloys, Al-Sb master alloys, and Al-Re master alloys are dried at 140-160° C.; (2) Melting and Modification: Coat the inner wall of the crucible with a slag remover, and preheat the crucible to 260-300°C. First, melt the aluminum ingot at 760-800°C, then add silicon ingot, magnesium ingot, Al-Cu master alloy, Al-Mn master alloy, Al-Cr master alloy, Al-Ti master alloy, Al-Sb master alloy, add the slag remover, and heat to melt. After all the alloys are melted, lower the melt temperature to 690-710°C, add Al-Re master alloy for modification, and stir evenly to obtain the aluminum alloy melt. (3) Refining: The aluminum alloy melt in step (2) is heated, and then the refining agent is pressed into the aluminum alloy in batches using a bell jar to about 1 / 2 below the melt surface, and the bell jar is rotated evenly and slowly in a clockwise direction. The refining time is 10-15 minutes; (4) Slag removal: After refining is completed, the bell jar is removed, the residual oxides are cleaned, and the inclusions on the surface of the aluminum alloy melt are removed with a slag scoop; (5) Semi-solidification of aluminum alloy solution: The aluminum alloy melt after slag removal is kept at 630-650°C for 5-10 minutes, and then a stirring and vibration method is used to prepare an aluminum alloy semi-solid slurry; (6) die-casting: die-casting the semi-solid aluminum alloy slurry obtained in step (5) to obtain a semi-solid die-cast aluminum alloy; (7) Solution heat treatment: The semi-solid die-cast aluminum alloy obtained in step (6) is solution treated at 570-590°C for 8-10 h, water quenched, and then aged at 210-230°C for 4-6 h. The semi-solid die-cast high-strength and high-toughness aluminum alloy is obtained after cooling in the furnace.

6. The method for preparing a semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 5, characterized in that: The slag cleaning agent in step (2) comprises sodium fluoride, potassium chloride and magnesium chloride, the mass ratio of the sodium fluoride, potassium chloride and magnesium chloride is 1:1:1, and the addition amount of the slag cleaning agent is 0.1-0.3% of the aluminum alloy melt.

7. The method for preparing a semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 5, characterized in that: The refining agent in step (3) is FF102 refining agent, and the aluminum alloy melt is heated to 730-740°C.

8. The method for preparing a semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 5, characterized in that: The stirring vibration method in step (5) is to perform ultrasonic vibration under the stirring of a graphite rotor, wherein the speed of the graphite rotor is 300-400 rpm, the ultrasonic vibration frequency is 60-80 Hz, and the ultrasonic vibration time is 15-25 s.

9. The method for preparing a semi-solid die-cast high-strength and high-toughness aluminum alloy according to claim 5, characterized in that: The die-casting temperature in step (6) is 200-300° C., the injection speed is 0.1-1 m / s, the injection pressure ratio is 30-50 MPa, the boost pressure is 60-80 MPa, and the holding time is 5-10 s.

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