Effects of LPSO Mg12YZn-Phase on Coefficient of Thermal Expansion and Mechanical Properties of Mg–Y–Zn Alloys

To enhance the progress of high performance Mg alloys, the effects of LPSO Mg12YZn-phase on coefficient of thermal expansion (CTE) and mechanical properties of Mg–Y–Zn alloys were investigated by relevant experiments in this study. The volume fractions of LPSO Mg12YZn-phase in Mg–1Y–0.5Zn, Mg–1.5Y–0.75Zn and Mg–2Y–1Zn alloys were 3.5, 6.5 and 9.3% respectively. The Mg–Y–Zn alloys had lower CTE than that of pure Mg and the CTE decreased with the Mg12YZn amount increase. The CTE of pure Mg is 26 × 10–6/K at room temperature, which is decreased to 21.95 × 10–6/K by adding 2 at % Y and 1 at % Zn. The CTE of three investigated alloys grew rapidly from 50 to 100°C due to no obvious plastic deformation in Mg matrix and Mg12YZn. The CTE increasing rate decreased sharply when the temperature was in the range of 100–300°C. The Mg–2Y–1Zn alloys exhibited highest CYS (157 MPa), UCS (338 MPa) and fracture elongation (27%) in three investigated alloys.