Microstructure, tensile and bending behaviour of the as-cast AM50 alloy modified with different antimony and copper additions

Abstract

The tensile and bending behaviours of the as-cast AM50 alloy were studied after adding different amounts of Sb/Cu (x = 0, 0.5, 1, 3 and 5 wt-%). The optimum levels of the Ultimate Tensile Strength (UTS) and tensile elongation (El%) values were found by adding 0.5 wt-% Sb and 0.5 wt-% Cu. The Yield Strength (YS) and hardness values improved with further additions of these elements. The tensile and hardness properties were investigated to be associated with microstructural features. With Sb additions, the new Mg3Sb2 intermetallics were formed. Moreover, by adding different Cu additions, three Cu-containing intermetallics were scrutinised by using the X-ray diffraction (XRD), thermodynamic calculations and also scanning electron microscopy (SEM). The formation of the new intermetallics could change the morphology of the β-Mg17Al12 phase and suppress its creation. Moreover, the grain refinement effects were different for each alloying element. Therefore, the grain refinement and the presence of new intermetallics had prominent impacts on the tensile and bending properties of the AM50 alloy. While grain refinement had a more positive effect on the UTS values, the YS and bending properties were chiefly controlled by morphology and size of intermetallics.