650℃で引張ひずみを付与したオーステナイト鋼のEBSDひずみ解析に及ぼす結晶粒径の影響

概要

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Tensile tests were conducted at 650°C on five different types of austenitic stainless steels varying in grain size. Each test was terminated at strain from 5 to 15 % followed by sample preparation for EBSD. Crystal direction at each point was measured by EBSD and misorientation was determined by Intra-granular Distortion, GOS (Grain Orientation Spread) and KAM (Kernel Average Misorientation). Plastic strain was found to be correlated with the results obtained by these methods, despite the differences in grain size and material type. At a certain plastic strain, Intra-granular Distortion indicated essentially the same result as that by GOS, since average crystal direction in a grain corresponds approximately to this direction at the center of a grain. Plastic strain was also seen to be correlated with results obtained by KAM, though the latter was noted to increase with reduction in grain size. KAM corresponded to the degree of misorientation within grains owing to dislocation density which has been seen to increase with reduction in grain size.