CN107267817A - A kind of high-strength antifatigue in-situ nano reinforced aluminium alloy and its pressure casting method - Google Patents

Abstract

The invention relates to an aluminum-based composite material, in particular to a high-strength anti-fatigue in-situ nano-reinforced aluminum alloy and a die-casting method thereof. Die castings are obtained through in-situ nano-strengthening and alloy composition regulation, combined with an optimized nonlinear high-pressure die-casting process. With the help of the in-situ nano-ZrB ₂ reinforcement and the scale effect, interface effect, and heterogeneous nucleation effect of the nano-Al ₃ Er precipitated phase, the strength, fatigue resistance, and damping properties of the alloy are significantly improved; at the same time, the Mg, Zn and Fe element content, and the introduction of Mn and Ni elements, while increasing the strengthening phase content and obtaining high strength, the harmful coarse precipitates such as Al-Fe are effectively refined and rounded, and the good die-casting performance of the alloy is ensured; Therefore, the components produced by the alloy of the invention and its die-casting method exhibit the characteristics of high strength plasticity, high fatigue resistance, high damping performance and good die-casting performance.

Description

A high-strength anti-fatigue in-situ nano-reinforced aluminum alloy and its die-casting method

technical field

The invention relates to an aluminum-based composite material, in particular to a high-strength anti-fatigue in-situ nano-reinforced aluminum alloy and a die-casting method thereof.

Background technique

With the development of economy and society, automobiles have gradually entered the homes of ordinary people and become an indispensable tool for people to travel and live. Statistics from the China Association of Automobile Manufacturers show that in 2016, a total of 10.5286 million Chinese brand passenger cars were sold, a year-on-year increase of 20.50%. The engine is the heart of the car, and the high efficiency, low cost and high performance of its key components have become the core of major car manufacturers to improve their product competitiveness.

With its advantages of high production efficiency, good economy, high casting precision and good surface finish, high-pressure casting gradually replaces high-cost low-pressure and gravity casting, and becomes the key to automobile engines such as aluminum engine cylinder blocks, oil pump housings, and shock absorbing components. The primary method of manufacturing the component. However, due to the high speed of liquid metal filling the cavity and the unstable flow state of high-pressure casting, the produced castings are prone to pores and cannot be heat-treated, resulting in the precipitated phases in the castings usually having a coarse needle-like or flaky structure, and the strengthening effect is not obvious. It is easy to produce stress concentration, making its strong plasticity and fatigue resistance low. As a result, it is difficult for high-pressure die castings to completely replace low-pressure castings and gravity castings, especially for mid-to-high-end automotive engines with high performance requirements.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing typical aluminum alloy AlSi9Cu3 for die-casting has low strong plasticity and fatigue resistance, and especially cannot meet the technical requirements of high-performance engine parts for its high strength, fatigue resistance and high damping. Composition control and in-situ nano-strengthening, combined with the optimized nonlinear high-pressure die-casting method, can increase the content of alloy precipitates, rounding and refining, and at the same time realize the in-situ nano-ceramic reinforcement strengthening in the grain and grain boundary, significantly improving Strong plasticity, fatigue resistance and damping properties of die-casting products.

The tensile strength of the vibration-absorbing support and the shell for the automobile engine produced by the technology of the invention can reach 352MPa, the yield strength can reach 285MPa, and the elongation can reach 10.6%. The final product has undergone a durability test on a special bench, and the minimum number of cycles has reached 1 million, which is much higher than the 500,000 times required by the customer. It has reached the DIN EN1706-1998 standard of German Volkswagen (shock absorbing bracket) and Japan Mazda (shock absorbing bracket) Shell) MES MM 621-ADC12 standard, and also exceeds the performance of the shock absorber bracket produced by low-pressure casting (after solid solution + aging heat treatment) (tensile strength 300MPa, yield strength 210MPa, elongation 7.5%).

An in-situ nano-strengthened aluminum alloy for die-casting with high strength, anti-fatigue and good damping performance and its die-casting method, through alloy composition control and in-situ nano-strengthening, combined with optimized nonlinear high-pressure die-casting to obtain intra-granular and grain boundaries Contains a large number of uniformly dispersed nano-ZrB ₂ ceramic reinforcements, contains nano-Al ₃ Er precipitates in the grain, and alloy precipitates including eutectic Si phase, Mg2Si phase, Al2Cu phase and Fe-containing phase are fine and round Die-casting pieces. With the aid of the dispersion strengthening of nano-reinforcement and nano-precipitated phase, interface damping effect and the grain refinement of Al ₃ Er phase produced by the low solid-solubility Er element in the alloy melt, the strong plasticity, fatigue resistance and Damping performance; at the same time, the increase of Mg, Zn and Fe element content, as well as the introduction of Mn and Ni elements, while ensuring good die-casting performance and increasing the content of alloy strengthening phase, can effectively refine and refine the alloy strengthening phase such as Al-Fe. Rounding; thus, the components produced by the alloy of the present invention exhibit the characteristics of high strength plasticity, high fatigue resistance and good damping performance.

The preparation method of the present invention comprises the following steps:

(1) Alloy smelting: Melt the AlSi9Cu3 alloy to 750-780°C and keep it warm for 10min. The AlSi9Cu3 alloy is a commercial alloy, and the mass percentages of its specific chemical composition are: Si 8.0-11.0, Cu 2.0-3.5, Zn 1.0-1.5, Mg 0.3-0.5, Fe≤0.8, Mn 0.1-0.5, the balance for Al.

(2) In situ synthesis of nano-ZrB ₂ nano-ceramic reinforcement: Add Al-Zr and Al-B master alloys to the melt smelted and kept warm in step (1) and rapidly heat up to 840-860 ° C, while using graphite stirring rotor Stir the melt to promote the full mixing of the alloy. The holding time is 10-15min, so that the Zr and B elements in the alloy react in situ under the driving force of free energy reduction to synthesize nano _- ZrB2 ceramic reinforcement, and then cool down to 730-750 ℃ and keep warm. Make the mass percent of zirconium and boron in the alloy in step (2) reach Zr: 3.0-5.0, B: 0.5-1.0.

(3) Introducing Er and Ni elements, adjusting the content of Fe and Mn elements in the alloy and refining and degassing: adding Al-Er, Al-Fe and Al-Mn master alloys and pure Ni to the composite melt obtained in step (2) In the body, the graphite stirring rotor is used to stir to promote the full mixing of the alloy, and the heat preservation and stirring time is 10-15min; then the powdered composite refining agent with a particle size of less than 500 μm is blown into the melt through the hollow channel of the graphite rotor with inert gas, Refining and degassing the melt to remove slag inclusions and hydrogen dissolved in the melt during high-temperature smelting and reaction of the alloy. The refining temperature is 730-750°C, and the refining holding time is 25-30min. Finally, the content of erbium-nickel-iron element in the alloy in step (3) reaches Er: 0.1-0.15, Fe: 1.0-1.5, Mn: 0.5-1.0, Ni 0.5-1.0.

(4) Adjusting the content of Mg and Zn elements: cooling the melt obtained in step (3) to 660-700° C. and keeping it warm, then pressing pure Mg and pure Zn into the melt after refining and degassing with a bell jar, Start the graphite stirring rotor, and stir at a slow speed. The heat preservation and stirring time is >15min, so that Mg and Zn can be dissolved into the alloy and prevent the melt from absorbing gas, and the content of magnesium and zinc in the alloy in step (4) can reach Mg: 0.5～1.0, Zn: 1.5-2.5.

(5) Non-linear high-pressure die-casting: Put the composite melt obtained in step (4) into the insulation bag of the die-casting machine, and use the optimized non-linear die-casting process for die-casting to obtain nano-composite reinforced die-castings, where the injection speed is from small to Large parabolic injection to realize the slow filling of 2.5-3m/s in the early stage, and the nonlinear filling of instantaneous high-speed filling at the end (the maximum injection speed reaches 40-50m/s, and the die-casting pressure reaches 100-150MPa).

(6) Aging treatment: The die-casting obtained in step (5) is subjected to aging treatment (natural aging or artificial aging), so as to obtain an in-situ nano-strengthened aluminum alloy die-casting with high strength, fatigue resistance and good damping performance.

The Al-Zr, Al-B, Al-Er, Al-Fe and Al-Mn master alloys are preferably master alloys with high content of alloying elements, such as Al-10Zr, Al-10B, Al-20Er, Al- 20Fe and Al-10Mn.

The in-situ synthesis of nano-ZrB2 nano _- ceramic reinforcement refers to the use of the low Gibbs free energy of ZrB2 in the multi _- element alloy system, and the thermodynamic-dynamic properties of Zr having low solubility and low thermal diffusivity in Al , after introducing Zr and B elements into the alloy, in _- situ synthesis of nanoscale ZrB2 ceramic particles in the melt, the size of which is 20-80nm, the content is 2-6wt.% of the alloy mass, and the synthesis temperature is 840-860°C . Therefore, in the solidification process of the alloy melt: on the one hand, the in-situ nano _- ZrB2 ceramic particles can be used as heterogeneous nucleation cores to improve the nucleation rate of the alloy, refine the grains, and finally include and disperse in the alloy grains, significantly improving The strength and fatigue resistance of the alloy; on the other hand, the nano _- ZrB2 ceramic particles that have not become the nucleation core will disperse at the grain boundary during the grain growth process, which can effectively pin the grain boundary and hinder the migration of the grain boundary. While improving the strength of the alloy, it maximizes the interface damping effect and improves the damping performance of the alloy.

The introduction of Er and Ni elements, adjusting the content of Fe and Mn elements in the alloy and refining and degassing refers to the introduction of 0.1-0.15wt.% Er in the alloy, on the one hand, by virtue of the low solubility of Er in the aluminum solution (0.1wt.%), the precipitation of Al ₃ Er heterogeneous nucleation cores in the alloy melt improves the nucleation rate of aluminum and refines the alloy. The fine L1 ₂ nano-Al ₃ Er precipitates that are finely matched with the aluminum matrix lattice are precipitated, which can significantly improve the aging strength and fatigue resistance of alloy die-casting parts; the purpose of increasing the content of Fe in the alloy is to increase the Fe content in the alloy. Precipitated phase content, while improving the strength of the alloy, further improve the anti-sticking performance of the alloy, avoiding the difficulty of demolding and sticking caused by the increase in the content of precipitated phases and the decrease in the expansion system of the alloy. The purpose of introducing Ni element and increasing the content of Mn element is Through the transformation of Ni, Mn and the needle-like β-Fe phase in the alloy into the bulk or Chinese character-like α-Al(Mn,Fe)Si and α-Al(Ni,Fe)Si phases, avoiding the increase of Fe content A large amount of acicular β-Fe phase reduces the ductility and toughness of the alloy.

The adjustment of the content of Mg and Zn elements is to further increase the content of the precipitated phase in the alloy to improve the strength and fatigue resistance of the alloy, and to improve the damping performance of the alloy by means of the increased phase boundary.

The non-linear high-pressure die-casting process refers to a new type of die-casting machine that adopts a programmable control of the speed of the die-casting cylinder, and optimizes the non-linear high-pressure die-casting process obtained to avoid turbulence and entrainment during the filling process of the melt , Facilitate the discharge of gas in the cavity and promote the infiltration and dispersion of nano-reinforcements under the instantaneous high-speed and high-pressure filling the cavity, so as to obtain die-casting products with less structural defects and excellent performance. Among them, the injection speed is parabolic injection from small to large, so as to realize the slow filling of 2.5-3m/s in the early stage, and the nonlinear filling of high-speed filling at the end (the maximum injection speed reaches 40-50m/s, and the die-casting pressure reach 100-150MPa).

Description of drawings

Fig. 1 (a) is the metallographic structure diagram of conventional AlSi9Cu3 die-casting parts, (b) is the metallographic structure diagram of the in-situ nano-strengthened aluminum alloy shock absorbing bracket die-casting parts with high strength anti-fatigue and good damping performance prepared by the present invention, from two gold It can be seen from the phase structure diagram that the needle-shaped precipitates in the die-casting parts prepared by this patent disappear and transform into granular or short-sheet-shaped rounded precipitates, which improves the dispersion of the precipitates and is beneficial to the strong plasticity and fatigue properties of the workpiece. improvement.

Fig. 2 The TEM structure diagram of the in-situ nano-reinforced aluminum alloy shock-absorbing bracket die-casting with high strength and fatigue resistance and good damping performance prepared by the present invention. It can be seen from the figure that the die-casting prepared by this patent has the intragranular and grain boundaries The existing in-situ nano-ZrB ₂ ceramic reinforcement phase and finer and uniform nano-Al ₃ Er nano-precipitated phase are beneficial to the comprehensive improvement of the workpiece's strong plasticity, fatigue resistance and damping performance.

detailed description

The embodiments of the present invention are further described below in conjunction with the accompanying drawings: the following examples are implemented on the premise of the technical solutions of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention is not limited to the following Example.

Example 1

Using Al-10Zr, Al-10B, Al-20Er, Al-20Fe, Al-10Mn master alloys and pure Ni, pure Mg, pure Zn, and AlSi9Cu3 as raw materials, the optimized non-linear high-pressure die-casting technology is used to prepare the automotive engine. Shock bracket.

The molten 500Kg commercial AlSi9Cu3 alloy (760°C) was transferred to the intermediate holding furnace, then the Al-10Zr and Al-10B intermediate alloys were added to the holding furnace and the temperature was raised to 850°C, while the graphite stirring rotor was used to stir the melt to promote the alloying process. Mix well, keep warm for 15min, then cool the alloy down to 750°C and keep warm; add Al-20Er, Al-20Fe, Al-10Mn and pure Ni into the melt, stir and keep warm for 15min, then put the powder with particle size less than 500μm Shaped composite refining agent blows inert gas into the melt through the hollow channel of the graphite rotor, and refines and degasses the melt to remove the slag inclusions generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. Refining The time is 30 minutes, the temperature is kept at 750°C, after the refining and degassing is completed, the temperature is lowered to 680°C and pure Mg and pure Zn are pressed into the refined and degassed melt with a bell jar, and the graphite stirring rotor is started and stirred at a slow speed. The heat preservation and stirring time is 18min, so that the final composition of the alloy reaches Si 9.5, Cu 3, Zr 3.5, B0.75, Zn 1.5, Mg 0.8, Fe 1.3, Mn 1.0, Ni 0.7, Er 0.12, and the balance is Al. Finally, the obtained Composite melt is used to prepare shock-absorbing bracket by optimized nonlinear high-pressure die-casting process. In the early stage, the mold is slowly filled at 3m/s to achieve advection filling and facilitate the smooth discharge of gas in the mold cavity. At the moment of full filling), increase the injection speed to 40m/s, and keep the pressure at 100MPa for 15s to obtain a die-casting shock absorber.

Put the die-casting blank with the sprue and flash removed into a heat treatment furnace for artificial aging. The aging temperature is 300°C and the aging time is 8 hours.

Sampling analysis shows that the shock absorber has a hardness greater than 97HBS, a tensile strength of 352MPa, a yield strength of 285MPa, and an elongation of 10.6%. The life of the compression fatigue test under a load of 7.6kN is greater than 2× ¹⁰ The durability test is carried out on a special bench, and the minimum number of cycles has reached 1 million, which is much higher than the customer's requirement of 500,000 times. The product meets the DIN EN1706-1998 standard of German Volkswagen (shock absorbing bracket) and the Japanese Mazda (shock absorbing shell) MES MM 621-ADC12 standard. As shown in Figure 1b, the metallographic structure diagram of the shock absorbing bracket prepared by the process of this example, it can be seen from the figure that compared with the conventional AlSi9Cu3 die casting, the needle-shaped precipitates in the die casting prepared by this patent disappear , into granular or short flake-like rounded precipitates, which improves the dispersion of the precipitates, which is beneficial to the improvement of the strong plasticity and fatigue properties of the workpiece. Fig. 2 is the TEM structure diagram of the shock-absorbing bracket die-casting prepared by the process of this embodiment, as can be seen from the figure, there are a large amount of in-situ nano _ZrB ceramic reinforcement phases in the grain and grain boundary of the die-casting prepared by this patent And the finer and uniform nano-Al ₃ Er nano-precipitated phase is beneficial to the comprehensive improvement of the workpiece's strong plasticity, fatigue resistance and damping performance.

Example 2

Using Al-10Zr, Al-5B, Al-10Er, Al-10Fe, Al-10Mn master alloys and pure Ni, pure Mg, pure Zn, and AlSi9Cu3 as raw materials, the optimized non-linear high-pressure die-casting technology is used to prepare the automotive engine. Shock shell (the shell structure is complex and difficult to fill and exhaust gas, usually reduce the Mg content, increase the die-casting pressure, improve the performance and yield of die-casting parts).

Transfer the molten 500Kg commercial AlSi9Cu3 alloy (750°C) into the intermediate holding furnace, then add the Al-10Zr and Al-5B intermediate alloys into the holding furnace and raise the temperature to 840°C, and at the same time use graphite stirring rotor to stir the melt to promote alloying Mix well, keep warm for 10min, then cool the alloy down to 740°C and keep warm; add Al-10Er, Al-10Fe, Al-10Mn and pure Ni into the melt, stir and keep warm for 10min, then put the powder with particle size less than 500μm Shaped composite refining agent blows inert gas into the melt through the hollow channel of the graphite rotor, and refines and degasses the melt to remove the slag inclusions generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. Refining The time is 25 minutes, the temperature is kept at 740°C, after the refining and degassing is completed, the temperature is lowered to 660°C and pure Mg and pure Zn are pressed into the melt after refining and degassing with a bell jar, and the graphite stirring rotor is started and stirred at a slow speed. Heat preservation and stirring for 20 minutes, so that the final composition of the alloy reaches Si 11, Cu 3.5, Zr 5.0, B 1.0, Zn2.0, Mg 0.5, Fe 1.5, Mn 1.0, Ni 0.5, Er 0.15, and the balance is Al. Finally, the obtained Composite melt is prepared by optimized nonlinear high-pressure die-casting process for damping shells, in which the mold is slowly filled at 5m/s in the early stage to achieve advection filling and facilitate the smooth discharge of gas in the mold cavity. After the cavity is full (riser At the moment when it is not filled), increase the injection speed to 50m/s, and keep the pressure at 150MPa for 15s to obtain a die-cast shock absorbing shell.

Put the die-casting blank with the sprue and flash removed into a heat treatment furnace for artificial aging. The aging temperature is 250°C and the aging time is 10 hours.

Sampling analysis shows that the hardness of the shock-absorbing bracket is greater than ^92HBS , the tensile strength has reached 315MPa, the yield strength has reached 243MPa, and the elongation rate is 8.9%. The durability test is carried out on a special bench, and the minimum number of cycles has reached 1 million, which is much higher than the customer's requirement of 500,000 times.

Example 3

Using Al-10Zr, Al-5B, Al-20Er, Al-20Fe, Al-5Mn master alloys and pure NIi, pure Mg, pure Zn, and AlSi9Cu3 as raw materials, using optimized nonlinear high-pressure die-casting technology to prepare oil pumps for automotive engines case.

Transfer the molten 500Kg commercial AlSi9Cu3 alloy (780°C) into the intermediate holding furnace, then add the Al-10Zr and Al-5B intermediate alloys into the holding furnace and raise the temperature to 860°C, and at the same time use graphite stirring rotor to agitate the melt to promote alloying Fully mixed, the holding time is 15min, then the alloy is cooled to 750°C and kept warm; Al-20Er, Al-20Fe and Al-50Mn and pure Ni are added to the melt, stirred and kept warm for 10min, and the ultrafine powder is refined The inert gas used as agent is blown into the melt through the hollow channel of the graphite rotor, and the melt is refined and degassed to remove the slag inclusions generated during the high-temperature melting and reaction of the alloy and the hydrogen dissolved in the melt. The refining time is 30 minutes , the temperature is kept at 750°C, and after refining and degassing, the temperature is lowered to 680°C and pure Mg and pure Zn are pressed into the melt after refining and degassing with a bell jar, and the graphite stirring rotor is started and stirred at a slow speed. 20min, make the final composition of the alloy reach Si 11, Cu 2.5, Zr 5.0, B 1.0, Zn 2.5, Mg 1.0, Fe 1.5, Mn 1.0, Ni 1.0, Er 0.1, the balance is Al, and finally the composite melt obtained is The oil pump casing is prepared by the optimized nonlinear high-pressure die-casting process, in which the mold is slowly filled at 4m/s in the early stage to achieve advection filling and facilitate the smooth discharge of gas in the mold cavity. , increase the injection speed to 50m/s, and keep the pressure at 130MPa for 15s to obtain a die-cast oil pump casing.

Put the die-casting blank with the sprue and flash removed into a heat treatment furnace for artificial aging. The aging temperature is 220°C and the aging time is 15 hours.

Sampling analysis shows that the shock absorber has a hardness greater than 93HBS, a tensile strength of 330MPa, a yield strength of 250MPa, and an elongation of 7.8%. The compression fatigue test life under a load of ^7.6kN is greater than 1.2×106 times. The durability test is carried out on a special bench, and the minimum number of cycles has reached 1 million, which is much higher than the customer's requirement of 500,000 times.

Comparative implementation

Comparative Example 1

Using AlSi9Cu3 alloy as raw material, the shock absorber bracket for automobile engine was prepared by optimized nonlinear high-pressure die-casting technology.

The melted 500Kg commercial AlSi9Cu3 alloy (700°C) was prepared by optimized nonlinear high-pressure die-casting technology to prepare shock absorbers for automobile engines, and artificially aged the die-casting blanks with the sprue and flash removed. The aging temperature was 300°C. The time is 8 hours.

Sampling analysis shows that the shock absorber has a hardness greater than 82HBS, a tensile strength of 285MPa, a yield strength of 193MPa, an elongation of 6.4%, and a compression fatigue test life of more than 1×10 ⁶ times under a load of 7.6kN.

Comparative Example 2

Using Al-10Zr, Al-10B, Al-20Er, Al-20Fe, Al-10Mn master alloys, pure Ni, pure Mg, pure Zn, and AlSi9Cu3 as raw materials, conventional die-casting technology is used to prepare shock absorbers for automobile engines.

The in-situ synthesis of nano-ZrB ₂ reinforcement and the control of alloy composition are the same as in Example 1. The obtained temperature is 680°C, and the composition is Si 9.5, Cu 3, Zr 3.5, B 0.75, Zn 1.5, Mg 0.8, Fe 1.3, Mn 1.0 , Ni 0.7, Er 0.12, and the alloy melt with the balance of Al, the die-casting shock absorber was obtained by conventional die-casting process.

The die casting was subjected to aging treatment using the same aging process as in Example 1.

Sampling analysis shows that the shock absorber has a hardness greater than 93HBS, a tensile strength of 335MPa, a yield strength of 263MPa, an elongation of 9.2%, and a compressive fatigue life of more than 1.8×10 ⁶ times under a load of 7.6kN.

Claims (7)

1. A high-strength anti-fatigue in-situ nano-strengthened aluminum alloy, characterized in that: through alloy composition control and in-situ nano-strengthening, combined with optimized nonlinear high-pressure die-casting to obtain a large amount of uniformly dispersed nano-ZrB in the grain and grain boundary ₂ ceramic reinforcement, containing nano-Al ₃ Er precipitates in the grain, and alloy precipitates including eutectic Si phase, Mg2Si phase, Al2Cu phase and Fe-containing phase are fine and round die-casting parts; the specific chemical composition The mass percentage of elements is: Si 8.0～11.0, Cu2.0～3.5, Zr 3.0-5.0, B 0.5-1.0, Zn 1.5～2.5, Mg 0.5～1.0, Fe 1.0～1.5, Mn 0.5～1.0, Ni 0.5～1.0 , Er 0.1-0.15, and the balance is Al; with the aid of the dispersion strengthening of nano-reinforcement and nano-precipitated phases, the interface damping effect, and the grain refinement of Al ₃ Er phase produced by the low solid solubility Er element in the alloy melt, Significantly improve the strong plasticity, fatigue resistance and damping performance of alloy components; at the same time, the increase of the content of Mg, Zn and Fe elements, and the introduction of Mn and Ni elements, while ensuring good die-casting performance and increasing the content of alloy strengthening phase, make The strengthening phase of alloys such as Al-Fe is effectively refined and rounded; thus, the strong plasticity, fatigue resistance and damping performance are synergistically improved. 2. The die-casting method of a kind of high-strength anti-fatigue in-situ nano-strengthened aluminum alloy as claimed in claim 1, characterized in that, the specific steps are as follows: (1) Alloy smelting: Melt the AlSi9Cu3 alloy to 750-780°C and keep it warm; the AlSi9Cu3 alloy is a commercial alloy, and the mass percentage of its specific chemical composition is: Si 8.0-11.0, Cu 2.0-3.5, Zn 1.0- 1.5, Mg0.3～0.5, Fe≤0.8, Mn 0.1～0.5, the balance is Al; (2) In situ synthesis of nano-ZrB ₂ nano-ceramic reinforcement: Add Al-Zr and Al-B master alloys to the melt smelted and kept warm in step (1) and rapidly heat up to 840-860 ° C, while using graphite stirring rotor Stir the melt to promote the full mixing of the alloy. The holding time is 10-15min, so that the Zr and B elements in the alloy react in situ under the driving force of free energy reduction to synthesize nano _- ZrB2 ceramic reinforcement, and then cool down to 730-750 ℃ and heat preservation, so that the mass percentage of zirconium and boron elements in the alloy in step (2) reaches Zr: 3.0-5.0, B: 0.5-1.0; (3) Introducing Er and Ni elements, adjusting the content of Fe and Mn elements in the alloy and refining and degassing: adding Al-Er, Al-Fe and Al-Mn master alloys and pure Ni to the composite melt obtained in step (2) In the body, the graphite stirring rotor is used to stir to promote the full mixing of the alloy, and the heat preservation and stirring time is 10-15min; then the powdered composite refining agent with a particle size of less than 500 μm is blown into the melt through the hollow channel of the graphite rotor with inert gas, Refining and degassing the melt to remove slag inclusions and hydrogen dissolved in the melt during high-temperature smelting and reaction of the alloy. The refining temperature is 730-750°C, and the refining holding time is 25-30min. Finally, the step ( 3) The content of erbium, nickel and iron elements in the alloy reaches Er: 0.1-0.15, Fe: 1.0-1.5, Mn: 0.5-1.0, Ni 0.5-1.0. (4) Adjusting the content of Mg and Zn elements: cooling the melt obtained in step (3) to 660-700° C. and keeping it warm, then pressing pure Mg and pure Zn into the melt after refining and degassing with a bell jar, Start the graphite stirring rotor, and stir at a slow speed. The heat preservation and stirring time is >15min, so that Mg and Zn can be dissolved into the alloy and prevent the melt from absorbing gas, and the content of magnesium and zinc in the alloy in step (4) can reach Mg: 0.5～1.0, Zn: 1.5～2.5; (5) Non-linear high-pressure die-casting: Put the composite melt obtained in step (4) into the insulation bag of the die-casting machine, and use the optimized non-linear die-casting process for die-casting to obtain nano-composite reinforced die-castings, where the injection speed is from small to Large parabolic injection; (6) Aging treatment: the die-casting obtained in step (5) is subjected to aging treatment to obtain an in-situ nano-strengthened aluminum alloy die-casting with high strength, fatigue resistance and good damping performance. 3. The die-casting method of a kind of high-strength anti-fatigue in-situ nano-strengthened aluminum alloy as claimed in claim 2, characterized in that, said Al-Zr, Al-B, Al-Er, Al-Fe and Al-Mn As the master alloy, the master alloy with high content of alloying elements is selected, specifically Al-10Zr, Al-10B, Al-20Er, Al-20Fe and Al-10Mn. 4. the die-casting method of a kind of high-strength anti-fatigue in-situ nano-reinforced aluminum alloy as claimed in claim 2, it is characterized in that, described in-situ synthesis nano ZrB ₂ nano-ceramic reinforcement refers to utilizing the multi-element alloy system _The Gibbs free energy of _ZrB2 is low, and Zr has low solubility and low thermal diffusivity in Al. Ceramic particles, the size of which is 20-80nm, the content is 2-6wt.% of the alloy mass, and the synthesis temperature is 840-860°C; thus in the solidification process of the alloy melt: on the one hand, the in-situ nano ZrB ₂ ceramic particles can be used as The heterogeneous nucleation core increases the nucleation rate of the alloy, refines the grains, and finally includes and disperses in the alloy grains, which significantly improves the strength and fatigue resistance of the alloy; on the other hand, the nano-ZrB ₂ that has not become the nucleation core Ceramic particles will disperse at the grain boundary during the grain growth process, which can effectively pin the grain boundary and hinder the migration of the grain boundary, improve the strength of the alloy, maximize the interface damping effect, and improve the damping performance of the alloy. 5. The die-casting method of a high-strength anti-fatigue in-situ nano-strengthened aluminum alloy as claimed in claim 2, characterized in that, introducing Er and Ni elements, adjusting the content of Fe and Mn elements in the alloy and refining and degassing , refers to the introduction of 0.1-0.15wt.% Er in the alloy. On the one hand, with the help of the low solubility of Er in the aluminum melt, Al ₃ Er heterogeneous nucleation cores are precipitated in the alloy melt to increase the nucleation rate of aluminum. Refining the alloy, on the other hand, solid-solubilized Er element in the alloy, will precipitate fine L1 ₂ type nano-Al ₃ Er precipitates in the grain during the aging of the alloy, which is well matched with the aluminum matrix lattice, and significantly improve the alloy die-casting. aging strength and fatigue resistance. 6. The die-casting method of a high-strength anti-fatigue in-situ nano-reinforced aluminum alloy as claimed in claim 2, wherein the content of Fe element is increased in the alloy to increase the content of Fe precipitates in the alloy and improve the strength of the alloy At the same time, further improve the anti-sticking performance of the alloy, and avoid the difficulty of demolding and mold sticking caused by the increase in the content of the alloy precipitates and the decrease in the expansion system; the purpose of introducing Ni and increasing the content of Mn is to pass Ni, Mn and the alloy The needle-like β-Fe phase transforms into massive or Chinese character-like α-Al(Mn,Fe)Si and α-Al(Ni,Fe)Si phases, avoiding the increase of Fe content to produce a large amount of needle-like β-Fe The phase reduces the plasticity and toughness of the alloy; the adjustment of the content of Mg and Zn elements is to further increase the content of the precipitated phase in the alloy, so as to improve the strength and fatigue resistance of the alloy, and improve the damping performance of the alloy by means of the increased phase boundary. 7. A die-casting method for high-strength and anti-fatigue in-situ nano-strengthened aluminum alloys as claimed in claim 2, wherein said nonlinear high-pressure die-casting process refers to a die-casting machine that adopts a programmable control of the speed of a die-casting cylinder , and optimize the obtained nonlinear high-pressure die-casting process to avoid turbulence and air entrainment during the filling process of the melt, facilitate the discharge of gas in the cavity, and promote the formation of nano-reinforcements under the instantaneous high-speed high-pressure filling the cavity Infiltration and dispersion to obtain die-casting products with less structural defects and excellent performance; the injection speed is a parabolic injection from small to large, so as to realize the slow filling of 2.5-3m/s in the early stage and the high-speed filling at the end. Linear filling, the maximum injection speed reaches 40-50m/s, and the die-casting pressure reaches 100-150MPa.