A good balance between strength and ductility in Mg–Zn–Mn-Gd alloy

Abstract

Microstructure evolution, dynamic recrystallization (DRX) behavior and mechanical properties of Mg–6Zn–1Mn-xGd alloys (x = 0, 0.2, 1.0 and 3.0 wt%) were investigated. The results showed that the phase components of as-cast Mg–6Zn–1Mn alloy were comprised of Mg7Zn3, α-Mn and α-Mg, while Mg3Zn6Gd (I phase) and Mg3Zn3Gd2 (W phase) were detected with the addition of Gd. Gd addition led to finer recrystallized grains, and it retarded DRX process due to the obstruction of nano-scale particles to grain boundaries. All as-extruded alloys exhibited typical basal texture, but Gd addition resulted in a low pole density of basal texture. Mg–6Zn–1Mn-3.0Gd alloy (ZMG613) exhibited a good balance between the strength and ductility with an ultimate tensile strength (UTS) of 354 MPa, yield strength (YS) of 306 MPa and elongation (EL) of 15.7%. Fine grain strengthening, second phase strengthening and dislocation strengthening were mostly contributed to the achievement of high strength. And the excellent ductility was mainly ascribed to the finer grains, weak basal texture, nano-scale I phase and non-basal slip activation.