Microstructure and mechanical characterisation of ECAP-ed ZE41A alloy

Abstract

The ZE41A magnesium alloy is used mainly for aerospace and automotive applications owing to its moderate strength up to 150 °C. However, it shows reduced strength and ductility at ambient temperature as a consequence of formation of stable ternary compound on grain boundaries. Therefore, obtaining improved mechanical properties by grain refinement and changing the distribution and size of ternary phase using equal-channel angular pressing constitute the objectives of the present work. The microstructure after four passes of ECAP is characterised by bimodal grain distribution, with parts of ultrafine grains or subgrains below 1 μm, and elongated larger ones, even above 20 μm. The significant change in distribution and size of ternary phase occurred after ECAP. In addition, the Zn22Zr particles of approximately 50 nm in diameter and less were determined. These precipitates were not previously identified in the EZ41A alloy. The grain refinement, as well as the redistribution and the fragmentation of the ternary phase particles through a ECAP process is accompanied by an increase in mechanical properties. The hardness is almost two times higher after 4 passes of ECAP compared to as-cast condition. The tensile strength, as well as the compression strength approximately doubles and the ductility is enhanced.