Controlling the microstructure of magnesium alloy sheet during rolling

A hot rolled magnesium alloy sheet embedded in a steel block was rolled together with 3% thickness reduction at room temperature, 373 K, and 673 K. Tensile twins were observed after the rolling, which could not be found when the magnesium alloy sheet was rolled without the steel block. The twin fraction was the highest at 373 K because of thermal expansion and activating non-basal slip systems at high temperature. Electron back-scattered diffraction analysis and finite element simulations confirmed that the steel block with higher strength played an important role in generating compressive stress along the transverse direction in the magnesium alloy sheet. The compressive stress could increase owing to suppression of thermal expansion in the magnesium alloy sheet at 373 K. The yield stress and the tensile stress became higher in the rolled specimen with the steel block at 373 K than in the specimen without it owing to grain refinement caused by tensile twins.