Microstructure evolution in hot deformation of 7050 aluminium alloy with coarse elongated grains

Hot deformation of 7050 aluminium alloy with coarse elongated grains has been investigated by tensile tests conducted at 340 and 460 degrees C and the strain rate of 1.0 x 10(-4) - 1.0 x 10-(1) s(-1). When the 7050 aluminium alloy was conducted at 460 degrees C and 1.0 x 10(-2) s(-1), the maximum elongation of 273% is achieved and large plastic deformation was carried out at an almost constant stress. The microstructure evolution under the deformation condition is characterised using OM, SEM, EBSD and TEM in detail. The results show that the microstructure evolution is realised by continuous dynamic recrystallisation in coarse grains. The increase in misorientation is proportional to the increase in the true strain, and the k value, the increasing rate of average misorientation angle, is 15.7 degrees. The primary hot deformation mechanisms of the 7050 aluminium alloy are localised grain boundary sliding and dislocation gliding, which can increase the grain boundary misorientation continuously.