Effect of die parameters on the grain size, mechanical properties and fracture mechanism of extruded AZ31 magnesium alloys

The study was carried out to evaluate the effect of extrusion ratio and extrusion die angle on the mechanical properties and microstructure of AZ31 magnesium alloy at 300 degrees C extrusion temperature with three different extrusion ratio of 1.77, 2.68, 3.55 and die angles of 10(0), 15(0), 20(0). It was identified that microstructure was significantly refined for all extrusion ratios. The average size was decreased to the range of 4.1 mu m-13.3 mu m from 22.4 mu m. By increasing extrusion ratio, it was observed that the tensile properties were considerably improved at room temperatures and tensile strength was reached to maximum 331 MPa after extrusion when initial measured value was 168.28 MPa. Significant grain refinement, enhanced mechanical strength and increase in microhardness values were observed with smaller die angles. It was observed that DRX mechanism is active and it supports the grain refinement. Dimples seen on the fractured surface were deeper that indicates the enhanced ductility of the material. Finally, among all the tests higher extrusion ratio with lower die angle gives better grain distribution in the microstructure and higher mechanical strength to the product.