Cyclic Deformation and Correspondent Crack Initiation at Low-Stress Amplitudes in Mg⁻Gd⁻Y⁻Zr Alloy

Cyclic deformation at low-stress amplitudes of a rare earth-containing magnesium alloy (Mg⁻Gd⁻Y⁻Zr) was investigated with emphasis on the responsible microstructural relationship between deformation mechanism and fatigue crack initiation. The results show that the microstructural deformation is extremely inhomogeneous at the low-stress amplitudes. Both deformation twinning and non-basal slip are barely observed, and basal slip is the predominant deformation to accommodate micro-plasticity. Fatigue crack initiation occurred at the basal slip bands, causing the morphology of facet on the fracture surface. Therefore, the basal slip is of prime importance in low-stress cyclic deformation and fatigue failure, and fatigue improvement could potentially be obtained through hindering the motion of basal dislocation by microstructural obstacles.