Microstructure and mechanical properties of high-pressure die cast pure copper

Microstructure and mechanical properties of high-pressure die-cast (HPDC) copper were investigated. The microstructure of the casting changed from surface to center due to the difference of the cooling rate. The as-cast microstructure comprised primary alpha-Cu grains and [Cu + Cu2O] eutectics. The primary alpha-Cu grains exhibited three types of morphologies including equiaxed, dendritic, and columnar. The mechanical properties of the casting were significantly influenced by the microstructure of the surface layer. The casting exhibited an ultimate tensile strength of 234 MPa (highest) when the skin layer comprised fine columnar dendrites, together with a yield strength of 87 MPa, and an elongation level of 25.4%. The samples exhibited an excellent elongation of similar to 56% with a skin of developed columnar grains. The difference of the skin layer was found mainly caused by the variation of the initial die temperature in HPDC.