The precipitation behavior of MgZn2 and Mg4Zn7 phase in Mg-6Zn (wt.%) alloy during equal-channel angular pressing

As-extruded Mg-6Zn (wt.%) Alloy was subjected to severe plastic deformation (SPD) by the equal-channel angular pressing(ECAP) at 160 oC. The results of tensile tests at room temperature showed that two passes ECAP resulted in a remarkable improvement of strength, yield strength from 200 to 265 MPa and ultimate tensile strength from 260 to 340 MPa. However, with the deformation increasing, the samples processed by ECAP for four or six passes had insignificant difference than that processed by two-pass ECAP. Massive precipitates were observed in all the Mg-6Zn alloys specimens processed by ECAP. Transmission electron microscope and X-ray diffraction results indicated that ECAP treatment induced the precipitation of laves MgZn2 phase and transition Mg4Zn7 phase. The spherical MgZn2 particles and irregular shape Mg4Zn7 particles coexist in the microstructure of Mg-6Zn alloy after six pass ECAP.