Mechanical properties and grain growth kinetics in magnesium alloy after accumulative compression bonding

An ultrafine-grained AZ31 magnesium alloy with a mean grain size less than 1 μm was fabricated using three-passes of accumulative compression bonding. Three passes were made at temperatures of 693 K, 643 K and 593 K, respectively, with a strain rate of 1.5 s−1 and a reduction of 75% for each pass. After the first pass, the mean grain size was abruptly refined from 23 μm to 5.1 μm and most of the basal planes had been rotated 90° perpendicular to the compression direction. After three passes, the microstructure was homogenous and excellent mechanical properties were obtained: 245 MPa yield stress, 372 MPa ultimate tensile strength and 14.8% fracture elongation. And a study on the kinetics of grain growth was carried out at temperatures range of 623–723 K. The effect of annealing temperature, T, and time, t, on the grain growth kinetics can be well interpreted by the kinetics equation image, where image. According to the experimental data, the activation energy for grain growth Eg was measured to be 105 kJ/mol.