Microstructure and Texture Evolution of 0.6 mm Ultra-Thin-Walled Tubes of Magnesium Alloys Fabricated by Multi-Pass Variable Wall Thickness Extrusion (VWTE)

摘要

AZ80+0.4%Ce alloy ultra-thin-walled tube with a wall thickness of 0.6 mm was fabricated by multi-pass variable wall thickness extrusion (VWTE) at 693 K. Microstructure and texture evolution were investigated. The results indicated that the average grain size decreased from ～47 μm of unprocessed alloy to ～8.9 μm after 5 passes VWTE. The total area reduction of Mg alloy tube was 91 %. Homogeneity of the microstructure was improved obviously and the morphology of Mg_(17)Al_(12) phases in coarse grains and fine DRX-ed grains exhibit lamellar and granular shapes, respectively. The VWTEed tubes showed a strong texture of (0001) planes, and the intensity decreased with deformation increasing to 4 passes. After 5p-VWTE, a strong texture characterized by (0001) pole tilting 20 degrees rotated from the normal direction (ED) towards the transverse direction (ND).