大ひずみ加工AZ31マグネシウム合金の超塑性変形 Superplasticity of AZ31 magnesium alloy processed by severe plastic deformation
Low temperature superplasticity was studied in a fine-grained magnesium alloy AZ31 which was processed by multi-directional forging (MDF) under decreasing temperature conditions. Tensile specimens were machined from MDFed Mg alloy parallel to the final compression axis. Tensile tests were carried out at temperatures from 393 K to 473 K and at various strain rates. Superplasticity appears even at 393 K with a stress exponent of around 5.6 and a total elongation of 370%. The relative large stress exponent can be connected with grain coarsening or refinement taking place during deformation. The initial texture introduced by MDF hardly changes during deformation. These suggest that grain boundary sliding can take place during superplasticity, while grain rotation hardly occurs.
軽金属 56(12), 716-720, 2006-12-30
The Japan Institute of Light Metals