Principles of grain refinement in magnesium alloys processed by equal-channel angular pressing

A model for grain refinement when magnesium alloys are processed by equal-channel angular pressing (ECAP) was reported. Optical microscopy was used to examine the microstructures and the average grain sizes were measured using the mean linear intercept method. Bimodal grain distributions are transitional in nature and they may evolve into homogenous grain distribution with increasing numbers of passes. This method is consistent with experimental results on the pressing of two magnesium alloys and with extensive data on processing of magnesium alloys in hot compression and hot torsion. Good results were obtained when pressing Mg alloys by ECAP with an initial high temperature and subsequent lower temperature due to initial processing at high temperature produces an intermediate grain refinement which is suitable for processing at lower temperatures.