Effect of Oxide Bifilms on the Fracture Behavior of AM60B Mg Alloy

Abstract

The effect of entrained Mg oxide bifilms on the tensile properties and fracture behavior of AM60B Mg alloy was studied. For this purpose, tensile specimens were prepared at different melt temperatures (670, 685, and 700 °C) and holding times (5, 10, and 15 min). According to the results, preparing the samples under non-optimal melting conditions increased the volume fraction of oxide bifilms and bifilm-related defects in the microstructure which reduced the tensile properties. The best tensile properties were obtained in the sample poured at 685 °C after holding for 10 min in the furnace in which the lowest amount of inclusions/bifilms was observed. The microstructural evaluations and fractography analyses showed that the most relevant bifilm-related mechanisms deteriorating the tensile properties were the reduction in the effective load-bearing cross section, facilitated formation of gas/shrinkage porosities, and increased nucleation of microcracks.