Fe-3.2wt.%Si合金単結晶の傾斜疲労き裂先端における繰返し変形のTEM観察

摘要

Local cyclic slip behavior around an oblique fatigue crack tip in single-crystalline Fe-3.2 wt.% Si alloy is precisely observed by using cross-sectional transmission electron microscopy (TEM). The observation successfully reveals the existence of different dislocation structures (vein, ladder, labyrinth, cell) around the crack tip. The results clearly suggest that the crack growth is strongly related to the formation of dislocation cell structures. Additional fractographic observation suggests that the crack growth, the path of which is found to be the boundary between hard cell region and soft matrix, accompanies the formation of striation pattern along the boundary.%負荷軸に対してほぼ垂直に進展するモードⅠ型疲労rnき裂（stage Ⅱき裂）については，その微視的進展機構がrnすべり面分離（slip-off)によるき裂先端開閉口であるこrnとが確認されている．一方，最大せん断応力とすべrnり面の影響を強く受け，巨視的に傾斜進展する混合モrnード型の疲労き裂については，せん断方向への微視的rn進展機構が材料因子に強く依存して複雑であり，不明rnな点が多い．