Microstructure and Mechanical Properties of Mg2Si Reinforced ZK60 Magnesium Alloy Deformed by ECAP

The effects of Equal Channel Angular Pressing (ECAP) on microstructure, mechanical properties at room temperature and high-temperature creep resistance of ZK60+2Si alloy were investigated. Results show that the components of as-cast alloy are mainly alpha-Mg matrix, Mg2Si and MgZn secondary phases. During ECAP processing, the original coarse Chinese-script Mg2Si phases are obviously broken into particles which tend to dispersively redistribute and the matrix is also been refined. After 4 passes of EACP, the tensile strength and the elongation of the alloy at room temperature increases from 154.8 MPa and 4.5% to 270 MPa and 17.5%, respectively. After 6 passes of EACP, the elongation further increases to 21%, but the tensile strength drops to 261 MPa. The high-temperature creep life of the alloy is extended from 20 h to 203 h, and the steady creep rate decreases by an order of magnitude. It is mainly because the tiny Mg2Si particles prevent grain boundary sliding effectively.