高氮奥氏体钢低温断裂途径与断口形貌

LOW TEMPERATURE FRACTURE PATH AND FRACTO- GRAPHY OF A HIGH NITROGEN BEARING AUSTENITIC STEEL

用扫描电子显微镜对18Cr-18Mn-0.7N高氮奥氏体钢低温断裂途径进行了观察,证实该钢低温脆断中裂纹既可穿晶扩展又可沿晶界和退火孪晶界扩展.仔细观察发现裂纹更容易在晶界和退火孪晶界形成并沿这些晶界扩展.对断面与侧面组织的双面观察表明,退火孪晶界断裂、沿晶断裂和穿晶断裂分别形成光滑平面状断裂刻面、光滑曲面状断裂刻面和粗糙不平的断裂刻面.

Fracture paths in low temperature brittle fracture of an 18Cr-18Mn-0.7N high nitrogen bearing austenitic steel were studied by means of scanning electronic microscopy. It is shown that the fracture propagates by either cracking through grain or along grain boundary and annealing twin boundary. Detailed investigation reveals that it is easier for cracks to initiate at grain boundaries and annealing twin boundaries and propagate along these boundaries. The dual-plane observations of fracture surface and adjacent side surface microstructures show that annealing twin boundary fracture, intergranular and transgranular cracking result in smooth planar facet, smoothly curved facet and rough facet, respectively.