High-Speed Impact Behavior and Microstructure Evolution of an Extruded Mg-7Sn-5Zn-3Al Alloy

Abstract

In this study, the high-speed impact behavior and microstructure evolution of an extruded Mg-7Sn-5Zn-3Al alloy were investigated under different strain rates (1626-4126 s−1) using a Split Hopkinson pressure bar. The experimental results indicated that the number of twins and dynamic recrystallization (DRX) increased, while the average grain size of the extruded alloy continuously decreased with the increase in the strain rates. In addition, the texture type of the extruded alloy transformed from (0001) to (11-20) during impacts. The high-speed impact behavior of the extruded alloy was found to strongly depend on the strain rate at room temperature. The strain rate sensitivity (SRS) changed from positive to negative with the increase in the strain rate. The negative SRS was mainly attributed to the DRX and the formation of micro-cracks at high strain rates (3712 s−1< $$\dot{\varepsilon }$$ < 4126 s−1). In addition, the elongation to failure ( $$\delta$$ ) and yield strength ( $$\sigma_{0.2}$$ ) of the extruded alloy increased, while the maximum strength ( $$\sigma_{ {\rm max} }$$ ) exhibited a nonlinear trend with the increase in the strain rates. The improved mechanical properties mainly originated from the grain refinement and texture strengthening. Multicrack propagation and intergranular quasi-cleavage fracture were the main dynamic fracture mechanisms of the extruded alloy during impacts.