The quantitative effects of temperature and cumulative strain on the mechanical properties of hot-extruded AZ80 Mg alloy during multi-directional forging

Abstract

There is still a lack of quantitative reports on the effects of temperature and strain on the mechanical properties of Mg alloy forgings. In order to investigate the quantitative effects of temperature and cumulative strain on the mechanical properties of AZ80 Mg alloy during multi-directional forging（MDF）, samples of the extruded alloy were multi-directionally forged (MDFed) at 380 °C, 280 °C and 180 °C with cumulative strain of 0.6 and MDFed at 180 °C with cumulative strains of 0.6, 1.2, 1.8 and 2.4. The microstructure and mechanical properties of the extruded alloy after MDF under different conditions were analyzed. The results show that MDF at different temperatures changes the mechanical properties of the alloy by affecting grain size, precipitates content and dislocation density. The higher yield strength (YS) and ultimate tensile strength (UTS) can be attained by MDF at lower temperature, but the YS and UTS are not sensitive to the cumulative strain when MDF at 180 °C. More coarse precipitates reduce the mechanical properties with the increase of the cumulative strain applied by MDF at 180 °C. The best balance of mechanical properties was attained after MDF at 180°Cwith the cumulative strain of 0.6. In this case, the YS, UTS（Engineering stress）and elongation of the AZ80 Mg alloy were 298.4 MPa, 402.1 MPa and 17.7%, which is mainly attributed to the formation of a bimodal microstructure.