Effects of extrusion ratio on the microstructure and mechanical properties of AZ31 Mg alloy

Experiments were conducted to evaluate the effects of extrusion ratio on grain refinement and subsequent mechanical properties at room temperature of AZ31 Mg alloy by backward extrusion. The backward extrusion was undertaken with extrusion ratio of 7, 24, 39, 70 and 100 at 250 °C. The results indicate with increasing extrusion ratio the grain of AZ31 Mg alloy is refined and the mechanical properties at room temperature are improved effectively. Further investigation shows that higher extrusion ratio (≥39) is more effective than lower extrusion ratio (≤24) to refine the grains. However, the efficiency of mechanical properties improvement at room temperature for high extrusion ratio is lower than that of low extrusion ratio. This study supports the idea that there exists a critical extrusion ratio for grain refinement and improvement of mechanical properties on certain conditions. Dynamic recrystallization and texture during extrusion are introduced to explain the effects of extrusion ratio on the microstructure and mechanical properties of AZ31 Mg alloy.