Prediction of grain size and yield strength of Mg-7Sn-1Al-1Zn alloys extruded at various temperatures and speeds

This paper analyzed the relationships between the extrusion conditions, grain size, and yield strength of an Mg-7Sn-1Al-1Zn alloy, which was extruded at different initial billet temperatures and ram speeds, and developed empirical models to predict the grain size and yield strengths. The results revealed that grain size increases as the extrusion temperature and ram speed increase, resulting in a decrease of the tensile and compressive yield strengths due to reduced effect of grain boundary strengthening. It was also found that the exit temperature is a key determinant of grain size and yield strength, i.e. as the exit temperature decreases, the grain size decreases while the tensile and compressive yield strengths increase. The grain size and yield strength prediction models, which provide results as a function of temperature and strain rate, were developed by considering the extrusion temperature and speed dependencies of the exit temperature, and the predicted results showed a good agreement with the experimental data.