Anisotropic microstructural evolutions of extruded ZK60 Mg alloy subjected to electropulsing treatment

Abstract

Electropulsing treatment (EPT) has attracted attentions as an alternative to a conventional furnace heat treatment (FHT). This study investigates the EPT effect on microstructural evolutions in α-Mg alloy. In particular, it clarifies the different kinetics in static recrystallization (SRX) and precipitation depending on the direction of EPT, namely ‘electropulsing anisotropy’, for the first time. EPT process induced an accelerated SRX than FHT in spite of the lower processing temperatures. EPT along the extrusion direction (EPT-ED) exhibited even faster completion of SRX within an hour compared to the process along the transverse direction (EPT-TD). The process also accompanied a faster dissolution of β′2 precipitates. Considering the applied processing temperatures, the athermal effect had a primary contribution to the enhanced microstructural evolutions by the EPT-ED process. EPT-induced charge imbalance improved a dislocation mobility, which increased an atomic diffusive flux. These factors were even intensified in case of EPT-ED than EPT-TD, thereby resulting in the mostly favored SRX and rapid dissolution of precipitates through the former.