Effect of reciprocating extrusion temperature and passes on the microstructural evolution of Mg-5Sn-1Si-0.8Y alloy

Abstract

AbstractIn this study, a reciprocating extrusion process (REP) was employed on Mg-5Sn-1Si-0.8Y magnesium alloy and the effect of the REP temperature (in the range of 340 °C to 400 °C) and number of REP passes (in the range of 2 to 8 at 340 °C) on the microstructural evolution of the alloy were investigated. The results show that the microstructure observed varied from edge to centre on the cross and longitudinal sections of the specimen. Upon increasing the extrusion temperature from 340 °C to 400 °C, the grain size distribution became uneven; the Mg2Si phase was concentrated at the grain boundaries, and the amount of Mg2Sn precipitated was reduced. In comparison with changing temperature, increasing the number of REP passes was more effective for improving the homogeneity of the alloy. With an increasing number of extrusion passes, the distributions for the grain size and second phases became increasingly uniform. In this study, an alloy subject to 8-REP passes and extrusion at 340 °C showed the finest and most homogeneous microstructure. Finally, a quantitative relationship between the REPed grain size and the Zener–Hollomon parameter was obtained.