Effect of various conditions on deformation twin formation by torsion and back-torsion

抄録

Magnesium alloys expected to be widely used as a component material of vehicle and high speed rail for sustainability because the advantages, lightweight properties and high recyclability. On the other hands, the magnesium wrought alloys are not used widely compared with casting alloys due to poor plastic workability from magnesium’s hexagonal close-packed crystal structure. In previous research, various material designs have been performed to improve the poor plastic workability in the wrought magnesium alloys such as ECAP, HPT. Among them, we studied torsion and back-torsion for magnesium alloy pipes. Our previous study clarified one of the factor in improvement workability was deformation twin formation. In the present study, we researched effect of various condition that torsion angle, varying rotating speed or heat-treated on deformation twin formation by torsion or back-torsion for clarify good design conditions of improve plastic workability of magnesium alloy pipes. We observed microstructure of twisted pipes by various conditions, and extracted deformation twin area. After that, deformation twin area ratio calculated from extracted area. The result shows deformation twin area increased with increasing torsion angle. In addition, the area of heat-treated back-torsion pipe was decreased from the not heat-treated pipe. Besides, the result shows the area of torsion or back-torsion pipes are less affected by rotating speed.