519 Cu-SiO_2 分散強化合金の高温疲労中の粒界破壊とメカニズム

Abstract

Orientation-controlled Cu-SiO_2 bicrystals having different misorientation angles were cyclically deformed at temperatures between 673K and 873K in vacuum. Although the fatigue lives of the most bicrystals tended to increase monotonically with decreasing stress amplitude at a higher stress amplitude region, some of them showed discontinuous and abrupt life shortening at a lower stress amplitude region. This transition of the cyclic ftigue behavior was brought by the occurrence of brittle intergranular fracture. This transition stress amplitude was also dependent on testing temperature and misorientation angle. At the lower stress region, elongated voids, which would be formed by GBS were observed at grain-boundary fracture surfaces. At the higher stress region, however, grain-boundary steps those were densely formed by plastic deformation of the matrices effectively suppressed GBS, resulting in the absence of brittle intergranular fracture.