Shear band formation during hot compression of AZ31 Mg alloy sheets

Abstract

Shear band formation has been reported to depend strongly on micro-structural factors, such as grain size, texture, alloying elements, and also on forming processes. The formation mechanism of shear bands has thus been investigated in the present work in relation to improve the forming limit of AZ31 Mg alloy. A series of compression tests have thus been carried out using strip-cast (SC) and hot-rolled (AR) AZ31 Mg alloys to compare their texture effects. The tests were performed under the strain rate of 10−1/s at room temperature (RT) and 300°C to clarify temperature dependence of shear band formation. Shear bands in SC specimens were observed to develop mainly at the boundaries of cast structures by generating compression twins and dynamic recrystallization (DRX) induced by the activation of the <a> and <c+a> slips as well as twinning at elevated temperatures. AR specimens exhibited, on the other hand, well-developed basal-fiber texture to generate shear bands through fine grains developed by DRX along the geometrically maximum shear stress directions.