高氮奥氏体钢低温断面的晶体学分析

用扫描电镜对18Cr-18Mn-0.7N高氮奥氏体钢的组织及低温脆断断面的晶体学特征进行了分析.结果表明:低温脆断断口上有退火孪晶界断面、沿晶断面及穿晶断面3种断裂刻面.退火孪晶界断面为一光滑、平坦的{111}面,上有折线状台阶,其它3组{111}面上的形变组织在退火孪晶界断面上形成3组交角为60°的直线状平行迹线;沿晶断面为一光滑曲面,{111}面的形变组织在其上形成几组不同交角的曲线状平行迹线;穿晶断面粗糙不平,显示平行于{111}面的台阶、河流花样或棱状花样,它们是不同{111}面上的裂纹在扩展中合并形成的.

CRYSTALLOGRAPHIC ANALYSIS OF THE FRACTURE FACETS IN LOW TEMPERATURE BRITTLE FRACTURE OF A HIGH NITROGEN BEARING AUSTENITIC STEEL

Microstructures and crystallographic features in low temperature brittle fracture of 18Cr-18Mn-0.7N high nitrogen bearing austenitic steel were investigated by means of scanning electronic microscopy. The results showed that there are three kinds of fracture facets on the fracture surface: annealing twin boundary fracture facet, intergranular fracture facet and transgranular fracture facet. Annealing twin boundary facture facet is one of planar and smooth {111} planes, with bent steps on it, and the planar deformations proceeding on the other three sets of {111} planes form a pattern of three sets of straight-lines intersected at 60º on the annealing twin boundary facet. Intergranular facture facet is a kind of smoothly curved facet on which the planar deformations proceeding on {111} planes form a pattern of several sets of curved parallel lines that intersect each other at different angles. Transgranular facture facet is rough and uneven, with steps parallel to {111} plane and river patterns or edge patterns on it, which is the consequence of coalescence of cracks propagating on different {111} planes.