Mechanical Properties and Microstructural Evolution of GTAW Welded Joints on Additively Manufactured Scalmalloy® and Extruded Aluminium Alloys

Abstract

Scalmalloy is an aluminium alloy developed for the additive manufacturing process of Selective Laser Melting. Size limitations often occurring in additive manufacturing due to chamber sizes can be overcome by welding parts together and to existing structures. In this paper, the feasibility of gas tungsten arc welding (GTAW) of Scalmalloy and welding Scalmalloy to extruded aluminium alloys using standard aluminium alloy GTAW parameters were demonstrated, and their resulting microstructures and mechanical properties reported. The welded microstructures showed coarse grains, porosity and other defects assumed to be due to unsuitable welding parameters and composition of materials. Tensile properties were much lower than the base metal values due to defects occurring due to welding. Scanning electron microscopy showed a ductile fracture surface with microvoid coalescence. Hardness testing across the welded samples showed softening of the metal in the Scalmalloy fusion zone and heat affected zones. Therefore, the welding parameters need to be optimized to improve mechanical properties and minimise defects.