ＬＰＳＯ相を有する高強度Ｍｇ－Ｚｎ－Ｙ合金の超高サイクル疲労破壊機構の解明

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In the proposed research, high cycle fatigue properties of an as-extruded Mg-10Gd-3Y-0.5Zr alloy was investigated by focusing on its fatigue crack initiation and early propagation behavior. As a result, several important phenomena were elucidated: (1) only basal slip was activated at low cyclic stress amplitude or in high cycle regime; (2) fatigue crack initiated from the slip bands along the basal plane, leading to the formation of cleavage-like facets on the fracture surface; (3) formation of facets around the crack initiation sites consumed a vast majority of the cyclic loadings in high cycle fatigue regime, and (4) small fatigue crack propagation was significantly retarded by local microstructure heterogeneity of neighboring grains. This can be ascribed to the incompatible deformation at low cyclic stresses, resulting in the localization of slip bands within isolated grains.