Effects of Ni and Zr on Microstructure and High Temperature Mechanical Properties of Al-Si-Cu-Mg Alloy
Al-Si-Cu-Mg hypereutectic piston alloy was prepared by metal mold casting.The volume fraction of heat resistant phase in different alloys was calculated by Thermo-Calc software.The microstructure of alloy was observed by scanning electron microscope(SEM)and transmission electron microscope(TEM),and the mechanical property test was carried out at 350℃.Effects of Ni and Zr contents on microstructure and mechanical properties of cast hyper-eutectic Al-Si-Cu-Mg piston alloy were investigated,and the relationships between morphology,area percentage of intermetallic compounds and mechanical properties were analyzed.The results indicate that the tensile strength and yield strength of Al-12.5Si-4.0Cu-1.0Mg alloy at 350℃are gradually increased and the elongation is gradually decreased with the increase of Ni content.The amount of Al3Ni and Al3CuNi phases is increased and the morphology is gradually tranformed from fine strip and rod to bulk and cluster,while the percentage of heat-resistant phase area is also increased obviously.With the increase of Zr content,the tensile strength and yield strength of Al-12.5Si-4Cu-1.0Mg-1.5Ni alloy are decreased firstly and then increased,while the elongation is increased gradually.The amount of AlSiNi Zr phase and volume fraction of heat-resistant phase are increased gradually.Al3Zr is precipitated along the alu-minum matrix[001]axis,and collocated with the aluminum matrix to form a high temperature strengthening phase,improving the high temperature strength of alloy by strengthening aluminum matrix.
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