Enhancing the high-cycle fatigue strength of Mg–9Al–1Zn casting by friction stir processing

Friction stir processing (FSP) of cast Mg–9Al–1Zn alloy plus subsequent aging produced a defect-free recrystallized fine-grained microstructure with fine β-Mg17Al12 particles. Compared to the as-cast parent material, the FSP sample exhibited significantly enhanced fatigue properties, with the fatigue strength being increased from ∼45 to ∼95 MPa and the fracture mode being changed from quasi-cleavage fracture to dimple fracture. The improvement was attributed to refinement of grains, elimination of porosities and coarse β networks, and precipitation of fine β particles.