Microstructures and mechanical properties of tungsten inert gas arc welded magnesium metal matrix composite (TiCp/AZ91D)

Abstract

Magnesium metal matrix composite (TiC_P/AZ91D) was joined by tungsten inert gas arc welding with addition of filler metal (TiC_P/AZ91D). The weld metal (WM) consists of TiC particulates, primary α-Mg and eutectic phases (eutectic α-Mg and eutectic β-Mg₁₇Al₁₂). TiC particulates distribute at primary α-Mg grain boundaries or inside the grains depending on the particulate size. At the grain boundaries, there exist divorced eutectic and lamellar eutectic microstructures due to rapid cooling rates. The pores accumulated are observed in the WM. In the heat affected zone, its microstructures have a coarsening tendency and microcracks form at the grain boundaries. The WM has the tensile strength of 140–190 MPa and the elongation of 1–3%. The tensile strength and elongation of welded joint are 130–160 MPa and 0–1% respectively. The pores accumulated, microcracks and grain coarsening are the main reasons to affect the mechanical properties of WM and welded joint.