Research For Micro-structure And Property Of High Silicon Aluminum Alloy Prepared By Composite Technology

High silicon-aluminum alloys are ideal casting materials, and the percent of silicon is beyond9%(wt%).They are well known for their low thermal expansion coefficient, big hardness, high thermal conductivity, good wear resistance and excellent casting forming. They are fit for Automobile air-condition compressor piston, cylinder, tail piston and pump parts, which wear and have good airproof. However, there are many defects in these alloys by ingot metallurgy and powder metallurgy technology. It refers to relatively coarse and bulks of Si particles in traditional casting alloys. The bad bond effect is caused by Al particles get oxidized in powder metallurgy, which greatly confine their application.Severe plastic deformation (SPD) has a good capacity of refining grains, which can reduce the material grains to sub-micro even to nano-scale ultra-fine grains material. The material in the deformation mainly shears. The bad plastic of high silicon-aluminum alloys in low temperature results in SPD undone. However, the rose small grains of material are obtained by control the pouring temperature, holding time and cooling rate in near-liquidus casting. Therefore, the near-liquidus casting is chose to the auxiliary process of SPD, which can provide the fine non-dendritic billets.The ultra-fine and better quality high silicon-aluminum alloy material is obtained by the composite technology of near-liquidus casting and multi-upsetting technology. The best process measure is matched by heating the high silicon-aluminum alloy raw materials to the temperature of720℃in crucible, holding time of1hour, pouring temperature of620℃, cutting the billets to cube, preheating the sample to the temperature of500℃, holding1hour in the resistance box furnace and carrying out the multi-upsetting process. To get the material of uniform micro-structure and mechanical property, the deformation amounts of each axis in upsetting should be equal. In addition, it is discussed the deformation mechanism of cylinder metal by two kinds of dynamics model.The rose small fine billets of high silicon-aluminum are obtained by near-liquidus casting. It is observed and summarized the effects of pouring temperature to the micro-structure, hardness, compressive strength and spectrum analysis. Secondly, it is discussed the feasibility of refining grains by one pass TE. At last, the billets of fine grain and good mechanical property are obtained by multi-upsetting. It is analyzed the effect of different deformation amounts and kinds and researched the mechanism of billets upsetting deformation.This method provides a new way of making high silicon-aluminum alloy material, which is suitable for having many dendrites in casting micro-structure or bad plastic and hard forming materials. The fine round and good quality high silicon-aluminum alloy materials have a wide application of plastic forming.