Microstructure evolution in magnesium alloy AZ31 during cyclic extrusion compression

The microstructure evolution of an AZ31 Mg alloy during cyclic extrusion compression (CEC) is investigated by optical microscopy, TEM and electron backscatter diffraction (EBSD). The mean grain size of 1.77 μm with fine grains of 150 ± 50 nm for AZ31 alloy is obtained after CEC 7 passes at 573 K. The colonies of fine grains have a representative grain size which decreases and develops a more homogeneous distribution with the increase of CEC accumulated strain. The fraction of low angle grain boundaries (LAGBs) tends to decrease while the average misorientation tends to increase with increasing number of CEC pass. Micro-textures are formed in AZ31 alloys during CEC and tend to be weaker as the CEC pass increases. A compound mechanism of grain refinement for magnesium alloys is introduced to explain the microstructure evolution during CEC processing.