Effect of ageing on microstructure and mechanical properties of a multi-directionally forged Mg-6Al-1Zn alloy

Samples of an AZ61Mg alloy were multi-directionally forged (MDFed) at room temperature employing small pass strains of Delta epsilon=0.1 to maximum cumulative strains of Sigma Delta epsilon =2.5. Ageing at 403 K for 1 h was carried out before and during MDFing. The coarse initial grains were gradually subdivided into ultrafine ones by mechanical twinning. Twin formation effectively suppressed the development of sharp texture and in this way enabled severe plastic deformation to take place at ambient temperature. Simple ageing of the MDFed sample lowered the strength. However, a combined process of ageing and MDFing increased the hardness and yield stress while it slightly decreased ductility. Good mechanical properties of 500 MPa yield stress, 540 MPa ultimate tensile strength and 4% plastic strain to fracture were achieved. (c) 2012 Elsevier B.V. All rights reserved.