Evaluation of fatigue life of AZ31 magnesium alloy fabricated by squeeze casting

Cyclic deformation behavior and fatigue life of squeeze-cast AZ31 magnesium alloy was studied under stress amplitude-control at room temperature. Low and high cycle fatigue tests with engineering stress amplitudes in the range from 40 to 110 MPa were conducted. Analysis of hysteresis curves was performed. Tension–compression asymmetry of hysteresis loops was not observed; the alloy exhibited cyclic hardening in tension and compression. The fatigue life in the low cycle fatigue region was expressed by Wöhler and derived Manson–Coffin curves. Experimental data in both, the low and high cycle fatigue regions were fitted by means of regression functions. S–N curves exhibited a smooth transition from the low to the high cycle fatigue regions and significant scattering of experimental points was observed. Furthermore, metallographic and fractographic analyses were performed. Crack initiation occurred from the specimen surface or on clusters of secondary particles; the region of final fracture was characterized by a transgranular ductile fracture. It can be concluded that the fatigue properties of squeeze cast magnesium alloy AZ31 are significantly improved comparing to materials prepared by common methods of casting. Squeeze casting also enables the cost-effective fabrication of complicatedly shaped parts.