Effect of liquation on the tensile properties of cast Mg–9Al–1Zn Alloy fusion welds

Abstract

This paper aims at understanding the role of liquation and solidification phenomena on the tensile properties of arc welded cast AZ91 magnesium alloy. Owing to its refined microstructure, the fusion zone exhibited improved ductility/strength compared to the base metal. It is demonstrated that the partially melted zone (PMZ) which is characterised by constitutional liquation of eutectic β-Mg₁₇Al₁₂ phase is the weakest link in the weldment. The reduced strength and ductility associated with the liquation phenomena are due to the increased volume fraction and thickness of the eutectic β-Mg₁₇Al₁₂ in the PMZ as well as the formation of liquation micro-cracks in a network of brittle intermetallic compounds. Controlling the liquation phenomena is critical for producing sound and reliable cast AZ91 arc welds.