EFFECTS OF CYCLIC EXPANSION-EXTRUSION WITH AN ASYMMETRICAL EXTRUSION CAVITY (CEE-AEC) ON THE MICROSTRUCTURE AND TEXTURE EVOLUTION OF Mg-13Gd-4Y-2Zn-0.5Zr ALLOYS

The effect of the passes of cyclic expansion-extrusion with an asymmetrical extrusion cavity (CEE-AEC) on the microstructure and texture evolution of the Mg-13Gd-4Y-2Zn-0.52r (w/%) alloy was investigated in this research. The alloy was subjected to (1. 2. 3 and 4) passes at (753. 733, 723 and 693) K, respectively. An optical microscope (OM), a scanning electron microscope (SEM) and electron backscattered diffraction (EBSD) were used to study the microstructure and texture evolution. The CEE-AEC process caused a significant grain refinement as the grain size decreased to 1.4 mu m from the initial value of 24 mu m after three CEE-AEC passes, while it increased slightly, to 1.6 mu m, after an additional CEE-AEC pass. With the increasing of the CEE-AEC passes, the number fraction (NF) of low-angle grain boundaries (LAGBs) tended to decrease, and the average misorientation increased due to the enhancement of recrystallization. The basal texture was weakened after four CEE-AEC passes, and the shear strain led to a rotation by 45 degrees. The maximum intensity was reduced from 11.692 to 1.944.