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 mu m 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 mu m to 5.1 mu m and most of the basal planes had been rotated 90 degrees 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 D-n - D-0(n) = kt, where k = k(0)e((-Eg/RT)). According to the experimental data, the activation energy for grain growth E-g was measured to be 105 kJ/mol. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.