Simultaneous improvements in strength and formability of modified Mg–2Zn alloys by alloying addition and twin-roll casting process

Abstract

The limited applicability of magnesium alloy sheets is attributed to the absence of strength and poor formability at room temperature. Strength is generally correlated to formability. It is crucial to achieve simultaneous improvements in both strength and formability. In this study, a novel Mg–2Zn based-alloy sheet was designed with modifications by adding particular alloying elements and processing via twin-roll casting (TRC) process. Microstructure evolutions during fabrication process in three experimental alloys were compared. The effects of alloying addition and TRC process on microstructure and mechanical properties were analyzed. The results showed that simultaneous improvements in strength and formability of Mg–2Zn were achieved, accompanied with excellent trade-off relationship between strength and formability in magnesium composition systems. Refined grain size, weakened basal texture and altered second phase type were obtained by alloying addition. Formation of high-density nanoscale particles with uniform distribution was the main benefit of using the TRC process. Under the promoted activation of prismatic <a> slip due to massive second phase particles, modified Mg–2Zn alloys exhibited weaker basal texture during the rolling process. The main strengthening mechanisms of modified Mg–2Zn alloys included grain refinement strengthening, grain boundary strengthening, and precipitation strengthening. Improvement of formability was attributed to weakened basal texture.