Effect of paint-bake like treatment on mechanical properties of Mg-Zn-Ca alloy

Abstract

Magnesium alloys are promising materials for the fabrication of automotive components due to their lightweight which could help car manufacturers reduce the amount of emissions generated per automobile and to meet present and future regulations of owning more environmentally friendly vehicles. However, the low strength of magnesium alloys compared to aluminium and steel have limited its usage and has necessitated the search for more potent strengtheningmechanism, like precipitation strengthening, to widen the application of magnesium alloys in the automotive industries. Precipitation hardening response of a Mg-4wt%Zn-0.3 wt%Ca(ZX40) alloy in an ageing process at 180 o C temperature typical of those used during paint baking cycle in automotive industries were studied using optical microscopy, Scanning electron microscopy (SEM), micro - hardness and thermoelectric power machine (TEP). Prior to the ageing process, one alloy was subjected to a 30 minutes solution heat treatment while the other sample was without solution heat treatment. Although, an initial decrease in hardness and strength of the alloy was observed due to solution treatment prior to ageing. The overall results showed that the mechanical (strength and hardness) and microstructure (fracture surface and precipitate formation) properties were enhanced in the 30 minutes solution treated sample s, which further emphasizes the need for solution treatment for better properties in an alloy. Keywords : Paint baking, Magnesium alloys, Precipitation strengthening, scanning electron microscopy