Optimisation of preheating and interpass temperature in WADED magnesium alloy AZ61: A comparative study on microstructure, residual stresses, and internal defects

Abstract

This study examines the effect of base material preheating on Wire Arc Direct Energy Deposition (WA-DED) of AZ61 magnesium alloy. The influence of preheating on the geometry and penetration behaviour of a single deposit was first evaluated and used to define suitable conditions for stabilising layer width in thin-walled structures. Two preheating strategies were examined, demonstrating that preheating the base material to 200C combined with the same interpass temperature provides the highest layer width stability and improved layer uniformity. The effect of preheating on residual stress was subsequently assessed through the analysis of base material deformation, revealing a reduction in residual stress of up to 50 % compared with fabrication without preheating. Furthermore, microstructural characterisation and µCT analysis were performed to investigate porosity formation mechanisms in the deposited material. Preheating was found to have a positive effect on wall thickness stabilisation, residual stress reduction, and porosity mitigation. Based on the combined evaluation of geometric stability, residual stress, and internal defects, a temperature of 250C was identified as the most suitable preheating and interpass temperature for WA-DED of AZ61 magnesium alloy.