Revealing the tensile anisotropy, tension–compression asymmetry, and strain-hardening behavior of a high-performance Mg–Gd–Ag alloy

Abstract

Abstract Mg–Gd–Ag-based alloys have attracted considerable attention in recent years owing to their high strength. However, their characteristic mechanical behavior remains unclear. Herein, the tensile anisotropy, tension–compression asymmetry, and strain-hardening behavior of a high-performance Mg–10.6Gd–2Ag (wt%) alloy fabricated by equal-channel angular pressing (ECAP) were systematically investigated and correlated with the evolution of microstructure and texture. The ECAP alloy exhibited synchronously enhanced tensile strength and ductility along all three directions compared with the as-cast alloy as well as improved compressive strength along the extrusion direction (ED) accompanied by slightly decreased ductility. In contrast to the pronounced reversed yield asymmetry for the as-cast alloy, the ECAP alloy exhibited a weak direct yield asymmetry along the ED. After aging, the tensile and compressive yield strengths of the ECAP alloy increased to 409 and 402 MPa, respectively, owing to the coprecipitation of basal γ'' and prismatic β' nanoplates, manifesting a near-symmetric yield response. Moreover, two strain-hardening stages (stage I and stage III) were detected in tensile deformation for all the investigated alloys, while all three stages were observed in compressive deformation. Both the strain-hardening ability and strength in the ECAP alloy before and after aging decreased slightly in the following order: ED > transverse direction (TD) > normal direction (ND), representing low anisotropy. In short, the present ECAP Mg–10.6Gd–2Ag alloy exhibited the advantages of high strength and ductility, near-symmetric yield response, and low anisotropy.