阅读说明：本技术 一种应用于汽车差速器支架的镁基复合材料的制备方法 (Preparation method of magnesium-based composite material applied to automobile differential support ) 是由 吉泽升 陈永生 崔鹏星 张勋 赵春芳 许红雨 胡茂良 张永冰 于 2020-07-20 设计创作，主要内容包括：一种应用于汽车差速器支架的镁基复合材料的制备方法,涉及一种应用于汽车差速器支架的复合材料的制备方法。本发明是要解决现有AZ91D镁合金替代铝合金用于汽车差速器支架强度不够的技术问题。本发明利用旋转喷吹双向搅拌添加高熵合金颗粒到AZ91D镁合金熔体,可以减少搅拌时间,破碎颗粒团聚效果显著；同时进行X和Y方向机械振动利于破碎边壁区的颗粒团聚,使边壁区颗粒随剪切搅拌到熔体中间,与熔体充分混合；料筒内金属液表面放筛网过滤氧化夹渣物,最后进行挤压铸造工艺制备产品。本发明高熵合金颗粒分散均匀,产品强度和硬度也得到大幅提高,产品内部无氧化夹渣物缺陷,颗粒与基体结合较好,能进一步拓宽镁基复合材料的应用情况。(A preparation method of a magnesium-based composite material applied to an automobile differential bracket relates to a preparation method of a composite material applied to an automobile differential bracket. The invention aims to solve the technical problem that the strength of the conventional AZ91D magnesium alloy for replacing aluminum alloy for the automobile differential bracket is insufficient. According to the invention, the high-entropy alloy particles are added to the AZ91D magnesium alloy melt by rotary blowing bidirectional stirring, so that the stirring time can be reduced, and the agglomeration effect of the broken particles is remarkable; meanwhile, the mechanical vibration in the X direction and the Y direction is beneficial to the particle agglomeration of the broken side wall area, so that the particles in the side wall area are sheared and stirred to the middle of the melt and are fully mixed with the melt; and (3) placing a screen on the surface of the molten metal in the charging barrel to filter the oxidized slag inclusion, and finally carrying out extrusion casting to prepare the product. The high-entropy alloy particles are uniformly dispersed, the strength and the hardness of the product are greatly improved, the defect of oxidation slag inclusion is avoided in the product, the particles are well combined with a matrix, and the application condition of the magnesium-based composite material can be further widened.)

1. A preparation method of a magnesium-based composite material applied to an automobile differential bracket is characterized by comprising the following steps:

firstly, smelting: placing a magnesium alloy AZ91D at the bottom of a smelting furnace, introducing protective gas or adding a flame-retardant covering agent into the furnace when the temperature in the furnace rises to 400-450 ℃, heating to 740-750 ℃, adding high-entropy alloy particles into a magnesium alloy melt under the conditions of rotary blowing bidirectional stirring and bidirectional stirring speeds of 100-400 rpm after the magnesium alloy AZ91D in the furnace is completely melted into a liquid state, then carrying out rotary blowing bidirectional stirring for 1-2 min and bidirectional stirring speeds of 100-400 rpm, and simultaneously carrying out mechanical vibration on the magnesium alloy melt in the X direction and the Y direction for 4-5 min by using a vibration table under the conditions of rotary blowing bidirectional stirring and bidirectional stirring speeds of 100-400 rpm to obtain a mixed melt;

the mass fraction of the high-entropy alloy particles in the mixed melt is 1-20%, and the diameter of the high-entropy alloy particles is less than 25 mu m;

the rotary blowing bidirectional stirring method comprises the following steps: carrying out rotary blowing and stirring on the magnesium alloy melt by using two rotary degassing machines, wherein the stirring directions of the two rotary degassing machines are opposite;

secondly, extrusion casting: uniformly spraying a release agent on the surfaces of a charging barrel and a die of an extrusion casting machine, quickly pouring the mixed melt prepared in the step one into the charging barrel, placing a screen on the surface of the mixed melt in the charging barrel, then carrying out extrusion casting, then opening the die, taking out a casting, taking out the screen, carrying out water cooling on the casting, polishing burrs and flashes, and cutting a pouring system to obtain the automobile differential bracket; the extrusion speed is 0.1-0.5 m/s, the extrusion pressure is 100-140 MPa, the pressure maintaining time is 10-30 s, and the mold temperature is 350-450 ℃.

2. The method for preparing the magnesium-based composite material applied to the automobile differential bracket as claimed in claim 1, wherein the high-entropy alloy particles in the step one are AlCoCrFeNi series, AlCoCrCuFeNi series or AlCoCuFeNi series.

3. The method as claimed in claim 1, wherein the flame retardant covering agent in the first step is RJ2 solvent.

4. The method as claimed in claim 1, wherein the frequency of the mechanical vibration in the first step is 50 Hz.

5. The method for preparing the magnesium-based composite material applied to the automobile differential gear bracket as claimed in claim 1, wherein the shielding gas in the step one is a gas formed by mixing sulfur hexafluoride and carbon dioxide according to a volume ratio of 1 (20-100).

6. The method as claimed in claim 1, wherein the gas used in the first step is one or a mixture of two of inert gases.

7. The method as claimed in claim 1, wherein the screen in the second step is made of stainless steel, has a diameter of 200-700 μm, and a diameter 1-2 mm smaller than that of the cylinder, and is preheated to 400-500 ℃ before use.

8. The method as claimed in claim 1, wherein the mold in the second step is two-part.

9. The method as claimed in claim 1, wherein the squeeze casting machine in the second step is a 350-ton squeeze casting machine.

Technical Field

The invention relates to a preparation method of a magnesium-based composite material applied to an automobile differential bracket.

Background

The magnesium alloy has the advantages of small density (about two thirds of aluminum alloy), high specific strength, good shock resistance and damping performance and the like, and has wide application prospect in the fields of automobiles and electronic products. However, the low hardness, low room temperature strength and plasticity of magnesium alloys greatly limit their applications. The magnesium-based composite material can eliminate or alleviate the disadvantages of the magnesium alloy. The process for adding the particle reinforced metal matrix composite material is simple, the cost is low, and if the SiC particles are added, the strength and the hardness of the magnesium alloy can be improved. Because the natural compatibility between metal and metal is good, the defect of poor wetting between ceramic particles and a matrix can be overcome by adding the metal particles into the liquid metal. The high-entropy alloy is a novel structural material and has excellent performances such as high strength, high toughness and the like, the wettability of the particles and a matrix can be improved by the high-entropy alloy particles, the performance of the magnesium alloy can be improved by preparing the high-entropy alloy particle reinforced magnesium-based composite material, and the application range of the magnesium alloy is expanded.

At present, the automobile differential bracket is used for solving the resonance problem of a vehicle in running. Most of automobile differential bracket parts are produced by aluminum alloy sand mold gravity casting or low-pressure casting, and in recent years, the differential bracket is produced by an aluminum alloy extrusion casting method. Compared with magnesium alloy, the aluminum alloy has high density, poor shock absorption, serious environmental pollution in aluminum alloy production and high oil consumption per kilometer, and hinders the lightweight development of automobiles. In order to widen the application condition of the magnesium alloy differential gear bracket, the comprehensive performance of the magnesium alloy differential gear bracket needs to be further improved, if the magnesium alloy automobile differential gear bracket can be developed by adopting a high-performance magnesium-based composite material and an extrusion casting method, the comprehensive performance and the internal quality of the magnesium alloy automobile differential gear bracket can be further improved, the damping performance and the strength of an automobile can be improved, and the development of light weight of automobile parts is promoted.

The extrusion casting is also called liquid die forging, is a near-net shaping method, and has good surface quality, no pore defect inside and good mechanical property. In the process of extrusion casting of magnesium alloy, because magnesium is active in property and is easy to react with oxygen, nitrogen, water vapor and the like in the smelting process, the magnesium alloy needs to be smelted for flame retardance and refining. Some oxides, flame retardants or refining agents and the like often remain inside the ingot, resulting in oxide and slag inclusion defects inside the casting. The existing extrusion casting magnesium alloy technology replaces the traditional extrusion casting technology to produce the aluminum alloy differential bracket, the appearance of the aluminum alloy differential bracket often has hot crack defects, and the thick and large parts of castings with flawless appearance can also have slag inclusion defects after being detected by X-ray, so that the performance of the magnesium alloy differential bracket is seriously influenced, and the high-speed development of the automobile industry is also hindered.

The rotary blowing stirring is usually to form gas-liquid vortex in the aluminum alloy or magnesium alloy melt by means of the fast rotation of the blowing head, to purify and degas and reduce the oxide inclusion in the melt. The conventional rotary blowing or stirring is only carried out in the middle of the melt, particle agglomeration easily exists at the positions of the side wall regions of the smelting furnace, the particles are not easy to stir uniformly, and the parts can not be effectively contacted with argon gas, so that the optimal refining effect can not be achieved. When the rotary blowing is stirred in the middle of the melt, the particles can be reasonably stirred along with bubbles, and the particles can be agglomerated along with the strong stirring of the melt due to the self-wrapping and adsorption effects, so that the particles are uniformly distributed and have good refining effect by means of stable and rapid stirring, which is always a difficult point.

Disclosure of Invention

The invention aims to solve the technical problem that the strength of an existing AZ91D magnesium alloy used for replacing an aluminum alloy for an automobile differential support is not enough, and provides a preparation method of a magnesium-based composite material applied to the automobile differential support, which realizes that the existing aluminum alloy differential support is replaced by the magnesium-based composite material automobile differential support, bidirectional rotary blowing and stirring are used in the magnesium-based composite material preparation process, the problem that the positions of the side wall area of a smelting furnace are easy to have uneven particle agglomeration and stirring is solved, the effects of uniform particle dispersion and melt all-position refining are achieved, a screen is arranged on the surface of a mixed melt in a charging barrel, the defects of slag inclusion and oxides are effectively filtered, and the effect of improving the strength and hardness is achieved by using an extrusion casting molding method, so that.

The preparation method of the magnesium-based composite material applied to the automobile differential bracket is carried out according to the following steps:

firstly, smelting: placing a magnesium alloy AZ91D at the bottom of a smelting furnace, introducing protective gas or adding a flame-retardant covering agent into the furnace when the temperature in the furnace rises to 400-450 ℃, heating to 740-750 ℃, adding high-entropy alloy particles into a magnesium alloy melt under the conditions of rotary blowing bidirectional stirring and bidirectional stirring speeds of 100-400 rpm after the magnesium alloy AZ91D in the furnace is completely melted into a liquid state, then carrying out rotary blowing bidirectional stirring for 1-2 min and bidirectional stirring speeds of 100-400 rpm, and simultaneously carrying out mechanical vibration on the magnesium alloy melt in the X direction and the Y direction for 4-5 min by using a vibration table under the conditions of rotary blowing bidirectional stirring and bidirectional stirring speeds of 100-400 rpm to obtain a mixed melt;

the mass fraction of the high-entropy alloy particles in the mixed melt is 1-20%, and the diameter of the high-entropy alloy particles is less than 25 mu m;

the rotary blowing bidirectional stirring method comprises the following steps: carrying out rotary blowing and stirring on the magnesium alloy melt by using two rotary degassing machines, wherein the stirring directions of the two rotary degassing machines are opposite;

secondly, extrusion casting: uniformly spraying a release agent on the surfaces of a charging barrel and a die of an extrusion casting machine, quickly pouring the mixed melt prepared in the step one into the charging barrel, placing a screen on the surface of the mixed melt in the charging barrel, then carrying out extrusion casting, then opening the die, taking out a casting, taking out the screen, carrying out water cooling on the casting, polishing burrs and flashes, and cutting a pouring system to obtain the automobile differential bracket; the extrusion speed is 0.1-0.5 m/s, the extrusion pressure is 100-140 MPa, the pressure maintaining time is 10-30 s, and the mold temperature is 350-450 ℃.

The invention has the advantages that:

the magnesium-based composite material automobile differential bracket has smaller material density, can greatly reduce the inertia force of parts, has better magnesium alloy shock resistance and damping performance, can greatly reduce the vibration of the parts, improves the comfort of vehicles, improves the functions and the application of the differential, is particularly applied to the light weight of automobiles, and widens the application field of magnesium alloy materials.

The invention belongs to a liquid method for preparing composite materials, high-entropy alloy particles are added into a magnesium matrix, the wetting effect of the high-entropy alloy particles and the magnesium matrix is good, crystal grains can be obviously refined, the hardness and the strength are improved, the strength reaches 235MPa, and the use requirement of an automobile differential bracket is met.

The invention adopts an extrusion casting method, has high casting precision, reduces subsequent processing links and has good process stability. The parts have no defects of shrinkage cavities and the like, the process yield is improved, the mechanical property of the castings is good, and the industrial mass production is met. Low consumption of resources and energy is realized, and economic benefit is promoted to be improved.

The invention utilizes the simultaneous operation of rotary blowing bidirectional stirring and mechanical vibration, is favorable for uniform dispersion of particles, is favorable for degassing and deslagging the melt, and has obvious effect on melt purification.

The invention utilizes rotary blowing bidirectional stirring, and simultaneously carries out shearing stirring in the positive and negative directions, thereby reducing the stirring time, shortening the production period, having remarkable agglomeration effect of broken particles, particularly the agglomeration of the particles at the positions of broken side wall areas, uniformly dispersing the particles, facilitating the dispersion of the melt at all positions, fully mixing the particles and the melt, and simultaneously facilitating the refining dehydrogenation of the melt at all positions.

The invention utilizes mechanical vibration, particularly mechanical vibration in the X direction (front and back) and the Y direction (left and right) simultaneously, has the advantages of breaking particle agglomeration in the side wall area, stirring the particles in the side wall area to the middle of the melt along with shearing, fully mixing with the melt, and simultaneously playing the roles of degassing and deslagging by the mechanical vibration.

The screen is arranged on the upper surface of the molten metal in the barrel of the extrusion casting machine to filter the oxidized slag inclusion, so that no slag inclusion or oxide exists in the part, and the extrusion casting with excellent mechanical property is favorably obtained.

Detailed Description