The Research Of Die-casting Process And Properties Of High Si Al-based Alloys

This paper aimed at three kinds of high Si Al-based alloys Al-10%Si,Al-20%Si and Al-30%Si alloy.The microstructure and mechanical properties of the products made of Al-Si alloys under liquid die casting are investigated and compared with those under normal casting.The die casting process of Al-Si alloys was developed on a cold chamber die casting machine.The effects of injection velocity,pouring temperature on the microstructure and mechanical properties of high Si Al-based alloys die casting were investigated.According to the optimized die casting process,the effects of the content of Si on the phase constitutions,microstructure,mechanical properties of Al-Si alloys were studied,fracture surface are analyzed by SEM.The experimental results demonstrated that:The liquid die casting have better mechanical property than that of the normal casing,and obviously refine the eutectic structure and the primary phases(primaryα-Al and Si phase),restrain the growth of primary Si phase.With the increase of the injection speed,for Al-10%Si and Al-20%Si alloys,the tensile strength,percentage elongation and impact toughness is increased firstly and then decreased,while HBS is decreased;For Al-30%Si alloy,the tensile strength,percentage elongation and impact toughness and HBS is increased firstly and then decreased.With the increase of the pouring temperature,for Al-10%Si and Al-20%Si alloys,the tensile strength, percentage elongation,impact toughness and HBS is increased firstly and then decreased;For Al-30%Si alloy,the tensile strength,percentage elongation,impact toughness and HBS is always increased.When injection velocity 2.5m/s,pouring temperature 720℃,mould temperature 150℃,work pressure 160Bar,the mechanical properties of Al-10%Si alloy:σ_b=233MPa,δ₅=8.57%,HBS=57.9;The mechanical properties of Al-20%Si alloy:σ_b=280MPa,δ₅=4.83%,A_k=25.56J/cm²,HBS=80.6.And injection velocity2.5m/s,pouring temperature 740℃were the optimized die casting process parameters for the Al-30%Si alloy,the mechanical properties of Al-30%Si alloy:σ_b=240MPa,δ₅=2.97%,A_k=15.95J/cm²,HBS=88.9.With the content of Si increasing,the magnitude of primary Si increased,the primary Si speediness growth.With the content of Si increasing,silicon is detrimental to the mechanical properties at room temperature when its content is more than 20%. Hardness can be improved.However,the percentage elongation and impact toughness is decreased.From the properties of high Si Al-based alloys,The alloy containing 20%Si possessed the best mechanical properties.