Microstructural Optimization of ZK60 Magnesium Alloy Through ECAP Processing Parameters

Abstract

This study examines the influence of Equal Channel Angular Pressing (ECAP) processing parameters on the microstructural evolution of ZK60 magnesium alloy, to identify the optimal conditions for achieving optimal grain refinement. Widely ZK60 recognized for its high specific strength its hexagonal close-packed (hcp) crystal structure limits slip activity and reduces ductility at room temperature. ECAP provides an effective means of imposing high shear strain without altering the billet dimensions, promoting dynamic recrystallization (DRX) and refining the microstructure. In this work, ZK60 billets were processed through a single ECAP pass at different temperatures (200, 275, and 350°C) and ram speeds (60, 300, and 480 mm/min). The results showed that low processing temperatures, particularly 200°C, combined with a low ram speed of 60 mm/min, yielded the highest degree of DRX and the finest equiaxed grains, with an average grain size of approximately 8 µm. Increasing temperature or RAM speed reduced the extent of grain refinement due to accelerated recovery and grain growth. Optical microscopy and XRD analyses confirmed that changes in grain size, phase distribution, ECAP temperature, and ram speed strongly control strain accumulation and DRX activity, and that the combination of 200°C and 60 mm/min provides the most effective conditions for microstructural optimization of the ZK60 alloy.