Effect of extrusion temperature on the microstructure and mechanical properties of hot-extruded ZK60 magnesium alloy

Abstract

ZK60 magnesium alloy was prepared by the hot-pressed sintering combined with the hot-extruded technique. The microstructure and mechanical properties evolution of ZK60 alloy with a reduced extrusion temperature from 350 °C to 250 °C were investigated in detailed. The extruded alloy was mainly composed of fine α-Mg grains and MgZn2 phase. The grains size gradually decreased with a reduction in extrusion temperature, and the yield strength obviously increased accordingly. The alloy extruded at 250 °C exhibited the smallest average grain size of 2.5 μm and the best combination of strength and plasticity, with a yield strength of 279 MPa and fracture strain of 18.1% in compressive condition, and 263 MPa and 13.7% in tensile condition, as well as a tension-compression yield asymmetry of 0.94. Both the fine grains formed by the continuous and twin induced dynamic crystallization mechanism and the precipitation strengthening contributed to the strength improvement.