Microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy fabricated by cold metal transfer wire arc additive manufacturing

Abstract

Wire arc additive manufacturing (WAAM) offers significant advantages in rapid manufacturing of complex integral parts. In this study, Mg-Gd-Y-Zn-Zr alloy deposited walls were fabricated by cold metal transfer (CMT) based WAAM. The interface bonding relationship between the additive zone and the substrate was studied, as well as the effect of the microstructure of the additive zone on the mechanical properties. The precipitated phase Mg24Y5 mainly distributed at the grain boundary was found in the additive zone of deposited walls, nano-scale contact interface and diffusion bonding interface were formed between β-Mg24Y5 and α-Mg (OR: [001]β-Mg24Y5//[10 1¯ 0]α-Mg), and a portion of the 18 R-LPSO phase to 14H-LPSO phase transition occurred in the substrate zone. In each layer of deposited metal, the bottom zone had a higher cooling rate than the top zone, which led to the supersaturation of rare earth elements. The precipitated phases between different deposition layers showed a decreasing trend from the bottom zone to the top zone due to the complex multiple thermal cycles in the additive manufacturing process. Compared with the cast Mg-Gd-Y-Zn-Zr alloy, the mechanical properties (UTS, YS and EL) of the Mg-Gd-Y-Zn-Zr alloy fabricated by WAAM were significantly increased. The ultimate tensile strength of the deposited walls along the travel direction was 227.27 MPa, and the elongation was 8.08 %.