Variation of Semi-Solid Microstructure and Mechanical Properties of Mg_98.5Ni_0.5Y_1.0 Alloy with Solidification Pressure

Abstract

A semisolid slurry of Mg98.5Ni0.5Y1.0 alloy was prepared by UV (ultrasonic vibration) method, then the slurry was cast under different squeeze pressures, in which the pressure varied from 0 MPa to 400 MPa. The results show that the primary α-Mg phase and LPSO structure (Long Period Stacking Ordered structure) of the alloy can be refined significantly. The solid solubility of Y and Ni elements in magnesium matrix can be increased with higher pressure, and the Mg2Ni particles is also precipitated out in LPSO structure under pressure. The grain size is decreased with the enhancement of squeeze pressure, which improves the strength. The alloy squeeze cast under pressure of 100 MPa has the highest cost performance. Its yield strength, tensile strength and elongation are 115 MPa, 243 MPa and 13.5%, and they are increased by 21.5%, 9.0% and 16.4% respectively compared with the alloy without applied pressure.