Examination of Cycling Rate Sensitivity in Magnesium Alloys in Fatigue and Corrosion Fatigue

Corrosion fatigue occurs when a metallic material undergoes mechanical cycling in the presence of a corrosive environment. Absorbable magnesium materials, intended to corrode in the body, may experience corrosion fatigue and must not fail prematurely because of it. Designing devices with appropriate data to predict how the material will behave is critical to success. Corrosion fatigue testing is complicated by mismatches between cycling frequency acceleration and corrosion acceleration. The aim of this study was to examine the fatigue and corrosion fatigue of three magnesium alloy wires (ZX10, LZ21, WE22) at a variety of strain levels and cycling frequencies. Baseline rotary beam (R = −1) fatigue testing was performed at three strain levels (0.5, 0.4, and 0.3%) and three frequencies (600, 3600, and 7200 rpm), in two environments (air, Hank’s solution). In general, cycles-to-failure increased with decreasing strain in all conditions, increased with cycling frequency at high but not low strains, and decreased in Hank’s solution compared to air. LZ21 displayed the highest corrosion fatigue durability, followed by WE22 and ZX10. These data will provide a baseline to aid designers in properly testing absorbable metal devices.