Effects Of Heat Treatment On Microstructure And Mechanical Performance Of Aluminum Alloy Engine Cylinder

Die casting aluminum alloys engine was popularized with the needs for lightweight and energy saving. Internal pores may formed due to air entrapment and oxide inclusion during die casting process, as a result of that, the distribution of eutectic Si and alloy elements of Al-Si-Cu alloys die castings can't be redistributed to strengthen castings through heat treated.Vacuum die casting was extensively applied to reduce internal pores of die castings, but there is little research of heat treatment of vacuum die casting. This paper researched effect of heat treatment on microstructure and mechanical properties,results shows as following:Vacuum die castings obtained more compact matrix, smaller and scatter pores compare with die castings, it makes internal pores hard to merge and grow up during heat treatment and weaker Ostwald Ripening of H-pores. Surface blister was delayed.Surface blister tends to occur later, when the distance between blister core and the surface is longer, its size is smaller, and it is in a higher density and strength matrix structure.Rule of eutectic Si redistribution is similar between vacuum die castings and die castings during heat treatment, solution treat 4 h at 500 ? achieved the best sphered morphology and turn bad beyond 4 h.Most of the Cu phase dissolved into the matrix after 4 h at 500 ? but Fe phase not even heat for a longer time.Tensile properties and elongation achieved the best stability after 500 ?×0.5 h + 150?×5 h heat treatment, become worse after 500 ?×2 h + 150?×5 h heat treatment.New internal pores formed during heat treatment, 7-8 times the density of internal pores as before specimens 500 ?×0.5 h + 150?×5 h heat treated.