High-strength and high-plasticity ZK60 magnesium alloy prepared by rapid solidification and high-speed extrusion

Abstract

The extrusion speed of ZK60 magnesium alloy is usually lower than 5 m/min. The rapidly solidified (RS) ZK60 magnesium alloy extruded at 350 ℃ with die-exit speeds of 10 m/min, 20 m/min and 30 m/min was investigated. The results reveal that after the RS ZK60 alloy was extruded at different die-exit speeds, the average size of dynamically recrystallized grains is 1.19–1.40 μm, the percent of high-angle grain boundaries (HAGBs) become larger with the average orientation degree of 57.83 ° to 54.81 °, the intensity of texture at (0001)<1̅100> is below 3.4, and the Schmid factors of the prismatic and pyramidal planes reach the high value of no lower than 0.42 overall, while no coarse MgZn phase was observed. The yield tensile strength, ultimate tensile strength and elongation of the RS as-extruded ZK60 magnesium alloy change slowly from 321 to 299 MPa, -355–348 MPa, and -23–27 % when the die-exit speed increase from 10 to 30 m/min, respectively. The ultra-fine grains and disappearance of the coarse low melting-point MgZn phase are the main reasons for the high-speed extrusion, high strength, high plasticity and low texture of the RS as-extruded ZK60 magnesium alloy.