Morphology Modification of Mg2Si by Solution Treatment and Its Effects on the Mechanical Properties of TiB2/Mg-4Al-1.5Si Composites

Abstract

TiB2/Mg-4Al-1.5Si magnesium matrix composites were prepared by semi-solid stirring assisted ultrasonic treatment, the primary Mg2Si phases in the composites exhibit polygon with sharp corners, and the eutectic Mg2Si phases appear thin Chinese-script or short-strip shape. To reduce stress concentration around the sharp corners (tips) of the Mg2Si phases, the morphology of the Mg2Si phases was further modified by solution treatment at 420 °C for 24 h, and the effects of the morphology modification of the Mg2Si phases on the mechanical properties of the composites were investigated. The results showed that after the solution treatment, the sharp corners of the primary Mg2Si phases were blunted, and the partial branches of the eutectic Mg2Si phases were dissolved into particles. The Vickers-hardness, ultimate tensile strength, yield strength, and elongation of the composites were increased by 11.50%, 33.28%, 28.57%, and 27.17% compared with those of unmodified composites, respectively. The solution treatment exhibits a more significant strengthening effect for the composites in hardness, ultimate tensile strength, and yield strength compared with the matrix alloys.