Fabrication Of Andalusite Reinforced Aluminum Matrix Composites

With the development of science,the overall performance of the metal are higher and higher required. Particle reinforced metal matrix composites because of low density, high strength, high modulus, high specific strength and high wear resistance, etc. has received wide attention and research. Andalusite is abundant in China, andalusite particles with thermal stability, wear resistance, high strength in high temperature, while the thermal expansion coefficient of andalusite particles is much smaller than the thermal expansion coeffcient of aluminum,and these advantages make it possible for andalusite to become An attractive particle reinforcement material.In this work,andalusite particle reinforced Al-alloy-matrix composites were prepared by stir casting.Mixing parameters on the distribution of composite particles were studied.For the problem of poor wetting between reinforcement and matrix alloy,we take a different pretreament on the reinforcemen and compare different pretreatment methods on the effect of adding reinforcement. the effect .The mechanical properties and density of the composites were also discussed.First, the test used water simulation method to determine the shape of the mixing paddle, mixing position, mixing directions and other issues. To fabricate composite materials by stirring casting, mixing parameters are important determinants, This study selected three parameters, namely, mixing speed, mixing time, mixing temperature, after Cross experiments by three parameters, by comparing the composite material microstructure to determine the optimal mixing parameters. The optimum mixing parameters are: mixing time of 10min, stirring speed of 1000r/min, mixing temperature of 720℃.In this experiment, using three method to compare the effects on the distribution of reinforcement,which are reinforcement added from the bottom,added from the top, and the method of stirring semi-solid. Compared the mechanical properties and structure .As the wettability of ceramic particles and aluminum is poor, using the preheating, coating aluminum processing, fluoride salt treatment to enhance their wettability. Found in three reinforcement approach can all improve the wettability,among which fluoride salt treatment is much better. To study the reinforcement particle size on the impact of composites, this study controlled reinforcement particle size by way of milling time and found that the longer the milling time increased with particle size smaller, the best milling time is 16h, The longer the milling time, the composite reinforcement particles agglomeration serious.Found by testing, enhanced hardness of the composites is inversely proportional to the size of particles; Amount of added reinforcement effect on the hardness increased firstly and then decreased;among Several preparation methods semi-solid mixing generated more pores and inclusions, the lower hardness than other alloy matrix. Density of the composite with reinforcements increased with increasing dosage, among the several preparation semi-solid mixing method with the lowest density...