Abstract
In the present study, fatigue tests were carried out to understand the influence of mechanical surface treatment on fatigue behavior of extruded AZ61 magnesium alloy at a stress ratio of -1 and frequency of 20 Hz under ambient environment. The mechanical surface treatments used in the present study were: (a) Shot-peening, (b) Micro-peening and (c) Barrel processing. From the results it was found that fatigue strength of shot-peened specimen degraded by about 30% compared to the bulk specimen. Cracks were nucleated from dents on the surface induced by shot-peening, which then propagated until final failure. On the contrary, both micro-peened and barrel processed specimens showed the same level of improvement in fatigue strength, which was about 15% higher than the bulk specimen. Though cracks were nucleated from the specimen surface with relatively small defects, the compressive residual stress induced near surface retarded the crack propagation, which was dominant for the improved fatigue strength.
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