The tensile properties at 448 K and the fracture behaviors under in situ transmission electron microscope strain for the Mg–6.0Gd–1.2Zn–0.15Y alloy

The precipitation hardening response and microstructure characteristics for Mg–5.95Gd–1.21Zn–0.15Y–0.46Zr (wt.%) were investigated during isothermal aging at 523 K. The results show that the alloy exhibits the remarkable age-hardening effect, and the precipitation γ″γ″ phase increases the hardness and strength of the alloy. In the tensile experiments at 448 K, the γ″γ″ phase cannot impede the twinning shear, and the twin traverses the γ″γ″ phase, which result in the γ″γ″ phase deflection at the twin boundary. The deflection angle was measured as about 4.2°. The in situ transmission electron microscope (TEM) tensile experiments were carried out to study the microcrack initiation, crack propagation as well as the interaction between the crack and γ″γ″ phases. It shows that the crack extension along the different crystal orientation of magnesium, result in the different of the thinning process of loaded crack tips and the crack growth mode. As the crack propagated vertical to the γ″γ″ phases, the prismatic plane split layer-by-layer along the [0 0 0 1]α.

► The Mg–6Gd–1.21Zn–0.15Y alloy exhibits the remarkable age-hardening effect.
► The twinning shear makes the γ″γ″ phase tilt about 4° at the twin boundary.
► As the crack propagates vertical to the γ″γ″ phases, the materials split layer-by-layer.
► The existence of γ″γ″ phase does not influence evidently the crack propagation manner.