Abstract
Extrusion was applied to AZ61A and AZ31B magnesium alloy billets with three different controlled conditions. As a result, it was found that the control of extrusion condition was one of the most effective approaches to attain grain refinement, because grain refinement took place in both alloys, where grain size decreased with decreasing outlet temperature, particularly remarkable in AZ31B for which the average grain size of approximately 2μm was obtained. Subsequently, roatating bending fatigue tests were performed using smooth specimens of the extruded materials in laboratory air at ambient temperature. In AZ61A, fatigue strength was not affected significantly by extrusion condition, while in AZ31B, it increased with decreasing outlet temeprature, i.e. grain size. The grain size dependence of fatigue strength could be described with the Hall-Petch relation in AZ31B, but not in AZ61A.
