Study On Microstructure And Properties Of ZA40Matrix Composites Reinforced With Si Particles

In this paper, ZA40alloy matrix composites reinforced by Si particles (Sip/ZA40composites) were fabricated by gravity casting and liquid extrusion process. To determine theproper technological parameters, the effects of liquid extrusion and modification technologyon the microstructure，mechanical properties and corrosion resistance of Sip/ZA40compositeswere investigated by optical microscope, scanning electron microscope, X-ray diffraction,tensile test, impact test, hardness test and wear test. This study has got some conclusions asfollows.The Sip/ZA40composites were prepared by gravity casting and liquid extrusion process.The microstructure and mechanical properties of composites were analyzed. The results showthat the composites made by liquid extrusion were better than gravity casting. The alpha phaseof the composites is equiaxial grain, the tissue of it is uniform and dense, and the size ofprimary silicon phase is about28μm, which has decreased by40%than gravity casting. It ismore regular and smaller and uniform distributed on the composites. Comparing with gravitycasting, the hardness, tensile strength, impact toughness, elongation, and wear resistance ofSip/ZA40composites prepared by liquid extrusion has improved by24.7%,24.7%,11.5%,11.8%and19%.The effects of different modification process on the microstructure and mechanicalproperty of ZA40-3%Si composites which made by liquid extrusion were studied, and themodifiers included mixed sodium salt and Al-P modifier. The results showed that underdifferent modification temperature, time and modifier content, the microstructure ofcomposites modified by Al-P modifier was uniformly, the size of primary silicon phase wasvery small. The best technological parameters on Al-P modification process are that thetemperature is820℃, the time is15minutes, the percentage of Al-P modifier is0.15%. Underthis process, the size of primary silicon is about11μm, which decreased by47%than mixedsodium salt modification. Comparing with mixed odium salt modifier, the hardness, tensilestrength, impact toughness and elongation of Sip/ZA40composites has improved by4.4%,5%,3.5%and3.8%, respectively.The effects of different corrosion medium on the Sip/ZA40composites′corrosion resistance were investigated by weight loss method, which the corrosion medium included0.5%HCl,0.5%NaOH and3.5%NaCl solution. The effects of different contents of Si,preparation process and modification process on the corrosion resistance of composites werestudied. The results show that the corrosion resistance of Sip/ZA40composites increasesfirstly then decreases with increasing contents of Si. When the content of Si is3%, thecorrosion resistance of composites is the best. Comparing with gravity casting, the corrosionresistance of composites made by liquid extrusion has improved by22.6%,30.5%and37.4%than gravity casting in0.5%HCl,0.5%NaOH and3.5%NaCl solution respectively. Thecorrosion resistance of composites made by liquid extrusion Al-P modification process hasimproved by10.8%than mixed odium salt in3.5%NaCl corrosion solution.