Effect of Grain Refinement on Fatigue Properties of Mg-0.3 at%Ca Alloy in Air and Simulated Body Fluid

We investigated the effect of grain refinement on the fatigue properties of biodegradable Mg-0.3 at%Ca alloy, which is expected to he applied in bone fixation devices. Mg-0.3 at%Ca alloy had poorer fatigue properties in simulated body fluid than in air, even after grain refinement. However, the alloy maintained mechanical properties similar to those of human cortical bone. Based on the fatigue fracture surface, the fracture modes of the Mg-0.3 at%Ca alloy differ markedly in air and simulated body fluid. In air, both transgranular and intragranular fractures occurred frequently, whereas in the simulated body fluid, intergranular fracture was the dominant mode. Although the effect of grain refinement on fatigue life was less pronounced in simulated body fluid than in air, the Mg-0.3 at%Ca alloy with grain refinement is considered a promising material for orthopedic devices.