Experiments ind-icate that the ductile-brittle transition phenomenon is closely associated with the mechanismof crack propagation and the crack tip blunting capacity.

• 应用扫描电镜观察了裂纹扩展的机制,发现结构钢低温韧脆转变现象的发生与裂纹塑性钝化的程度有直接关系,表现在延伸带的宽度发生很大的变化。