Study on mechanism of grain boundary embrittlement of austenitic stainless steel after irradiation using in-situ monitoring system of grain boundary separation

通过高温固溶退火和He注入Fe-15Cr-20Ni的晶界观察，研究了奥氏体不锈钢在拉伸状态下的氦脆行为。得到了以下结果。在923和1023K下，弹性变形区出现晶界分离。只有在823K屈服后才能观察到分离的晶界，而在723K以下则没有观察到。这些分离的晶界是随机的或更高的晶界，其方向与应力方向接近垂直。随着塑性应变的增加，观察到下西格玛晶界的分离。随着外加应变的增加，分离的晶界连接在一起，并在试件断裂前形成晶界裂纹。设计制作了拉伸试验过程中表面裂纹形成的现场观测系统，并对其变形模式进行了分析。

Helium embrittlement of austenitic stainless steel by tensile mode was investigated though grain boundary observation of solution-annealed and He-implanted Fe-15Cr-20Ni at high temperature. The following results were obtained. Grain boundary separation appeared during the elastic deformation area at 923 and 1023K. The separated grain boundaries were observed only after yielding tested at 823K, and these were not observed below 723K. These separated grain boundaries were random or higher grain boundaries and their direction was near perpendicularly to the stress direction. With increasing plastic strain, separated grain boundaries of lower sigma boundaries were observed. With increasing the applied strain, separated grain boundaries were linked and formed grain boundary cracks and before the specimen rupture. In-situ observation system for surface crack formation during tensile test was designed and manufactured, and the analysis of deformation mode is under investigated.