Abstract
Cast aluminum alloy, AC4CH-T6, was microstructurally-modified by friction stir process (FSP) with two different conditions of strain rates and plane bending fatigue tests were performed to investigate the effect of process condition on the fatigue behavior. The tool traveling speed was set to be constant, 150 mm/min and the tool rotational speeds were set to be 500 and 1000 rpm. Casting defects were eliminated and the fine grains were obtained by the FSP. Grains became finer in specimen FSPed in lower strain rate compared with that FSPed in higher strain rate. The fatigue strengths of FSPed specimens were highly improved compared with the as-cast material, which is attributed to the elimination of casting defects and the grain refinement. The fatigue strength of the specimen FSPed in lower strain rate was higher than that FSPed in higher strain rate. EBSD analyses revealed that the strong texture was formed in the FSPed specimen along which fatigue crack grew.
