MICROSTRUCTURAL DESIGN OF Mg ALLOYS FOR LIGHTWEIGHT STRUCTURAL APPLICATIONS
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Under a carefully selected starting texture, Mg-3Al-1Zn (AZ31) has been successfully processed via equal channel angular processing (ECAP) at 150C under multiple passes to obtain an ultra-fine grained bulk material. The multiple ECAP passes at 150C decreased the grain size of bulk as-received AZ31 from 25 m to 0.8 m. Upon grain refinement, the tension-compression yield asymmetry decreased, and the yield strength increased to the level of 6000 series Al alloys. Detailed electron backscatter diffraction (EBSD) analyses clearly indicated that the formation of compression twins initiated deformation localization via softest basal slip. Subsequently, dynamic recrystallization initiated within the compression twins for temperatures at 150C and below. Thus, the preferential sites for softest basal slip cause local softening and DRX, accumulating throughout the material in the form of large shear bands which lead to failure during ECAP.