(Al₃Zr+Al₂O₃)_p/A356 Composites' Structure And Performance In Different Electromagnetic Field And Casting Technics

Particle reinforced aluminum matrix composites have excellent mechanics and physics performance such as high specific strength, high specific stiffness, wearable, antifatigue, low coefficient of thermal expansion, low density, high tiny yield strength, well dimensional stability and heat conductivity. They can be widely used in aviation, spaceflight, military affairs, automobile, electron, athletic field and so on. However, the conventional method of synthesized composites, which have big particle size, polluted particle surface, bad combined interface and easily generated product defects and series of weakness, which limited its enormously application.In this paper, the author studied Al-Zr-O system and electromagnetic field was introduced in the course of in-situ synthesizing composites, and used melt reaction to synthesize composites. The results showed that: The (Al₃Zr+Al₂O₃)_p/A356 composites synthesized with electromagnetic stirring have a number of reinforcement, which wan small and dispersed in the matrix. The composites wear properties was better than the composites synthesized without electromagnetic stirring, in 60 minutes the wear loss of composites synthesized without electromagnetic stirring was 30.23mg, but with electromagnetic stirring was only 24.94mg. just 82.5% of composites was synthesized by conventional techniques. High-frequency pulse magnetic fields can improve the thermodynamic conditions of Zr(CO₃)₂-A1 system, aggravating in-situ reaction, which can also increase the number of nuclear-shaped, reinforcing the volume fraction of reinforcement, and high-frequency pulsed magnetic field can weaken the "skin effect" of field intensity distribution and enhance particles evenly distribution.(Al₃r+Al₂O₃)p/A356 composites molded by different conditions will have a great difference in structure and properties. Molding by conventional metal mould casting, the composites' structure has many casting defects such as porosity and shrinkage cavity, its mechanical properties was very poor. Molding by semi-continuous casting, its particles was relatively small, but reunited. Molding by squeeze casting, the composites have dense structure, porosity, shrinkage cavity and other casting defects decreased significantly, and the mechanical properties has been greatly improved. Its tensile strength improved about 127% and specific elongation increased 59% relative to the metal-casting composites. In 120 minutes wear time, the metal mould casting molded composites' wear loss was 66.46mg, but squeeze casting molded composites' was only 39.78mg, merely 59.9% of composites molding by metal mould casting.