Improving room-temperature ductility of a Mg–Zn–Ca alloy through friction stir processing

Abstract

The effect of friction stir processing (FSP) on the microstructure evolution and mechanical properties of as-cast Mg–Zn–Ca (Mg-1.2wt%Zn-0.1wt%Ca) alloy was investigated. The result shows that the average grain size of the stir zone is greatly refined from ∼170 μm to ∼13 μm. Moreover, a basal texture is formed in the stir zone, and the c-axis of the grain is tilted to the normal direction about 42.6° away from the processing direction. Although the tensile strength has little improvement compared to the as-cast alloy, the elongation is increased from 24.6% to 45.4%. The excellent room-temperature ductility of the FSP alloy is mainly attributed to the fine grain size and the preferential orientation of the grains in the stir zone. The Schmid factor up to 0.44 means that basal slip is beneficial to be activated, resulting in a high elongation.