Microstructures and strengthening mechanisms of Mg-8.2Gd-4.6Y-1.5Zn-0.4Zr alloy containing LPSO, β′ and γ type phases

Abstract

The microstructures and strengthening mechanisms of the Mg-8.2Gd-4.6Y-1.5Zn-0.4Zr (wt%) alloy with long-period stacking ordered (LPSO), β′ and γ type phases were systematically studied. The results show that the LPSO with lamellar and block structures forms near the grain boundaries. The grains are clearly refined, and the 18R LPSO phase is oriented along the extrusion direction after extrusion. Some particles also precipitate from the Mg matrix dynamically. The extruded alloy exhibits a remarkable age-hardening response, and mechanical properties, with a tensile strength (TS) of 449 MPa, yield strength (YS) of 362 MPa, and elongation of 7.9% obtained in the peak-aged alloy. The strengthening mechanisms of the alloy in different states are discussed. Grain boundary and precipitation strengthening are the main strengthening mechanisms for the peak-aged alloy.