相界面对核电Z3CN20-09M不锈钢裂纹萌生和扩展的影响

为研究国产核级主管道不锈钢Z3CN20-09M中奥氏体/铁素体相界面在裂纹萌生与扩展过程中的作用,通过扫描电镜原位拉伸技术对核级主管道不锈钢在拉伸过程中的组织形变、微裂纹的萌生与扩展进行原位观察,对断口进行了分析.研究表明,在拉伸过程中,微裂纹优先在杂质颗粒和相界位置萌生.当铁素体/奥氏体界面垂直于拉伸方向时,裂纹倾向于沿相界萌生,并沿相界扩展；当铁素体/奥氏体界面平行于拉伸方向时,微裂纹在相界开裂,并垂直于界面扩展,主裂纹发生偏折,界面在裂纹扩展过程中起阻碍作用.

Effect of phase boundary on nucleation and propagation of microcrack in nuclear grade Z3CN20-09M stainless steel

To study the effect of ferrite and austenite phase boundary on nucleation and propagation of microcracks in nuclear grade Z3CN20-09M stainless steel, in-situ SEM tensile technique was used to study deformation, nucleation and propagation of microcracks in Z3CN20-09M stainless steel during tension, and the fractography was subsequently analyzed. The results indicated that the microcracks were formed in the phase boundary and impurity particle positions during tension. In the case of phase boundary perpendicular to loading direction, microcracks nucleated and propagated along phase boundary; while for the phase boundary parallel to loading direction, microcracks nucleated at phase boundary propagated perpendicularly to phase boundary, and the main crack easily deflected. In this condition, the phase boundary played a hindrance effect on crack propagation.