Abstract
The microstructure heterogeneity of high pressure die casting (HPDC) Al-8Si-0.5Mg-0.2Cu-2Zn alloy was modified by optimizing the characteristic of externally solidified crystals (ESCs), and their effect on mechanical behavior were also discussed. The results revealed that the formation of microstructure heterogeneity in HPDC alloys was significantly depended on the characteristic of ESCs. In addition, the characteristic of ESCs could be modified by the melt superheat treatment before slow shot process. The morphology of ESCs is dendritic and the distribution show serious segregation at pouring temperature of 685 °C and 725 °C, but evolved to regular and uniformly at pouring temperature of 705 °C. The uniform distribution and regular ESCs leads to uniform stress concentration during tensile deformation at pouring temperature of 705 °C. The cracks mainly initiated at interfacial region of the clustered ESCs, and the obtained yield strength161MPa and ultimate tensile strength 307 MPa, meanwhile, the elongation maintain a high value of 11.4%.
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