图为DZ2（0.05V0Nb）钢在不同温度下的低温拉伸端口形貌图，由图可知，DZ2（0.05V0Nb）钢随着试验温度的降低，断口撕裂棱减少，温度低于-60℃时，开始出现纵深裂纹，图中给出了试验温度-100℃拉伸断口微观形貌，可见断口上分布着大量韧窝，说明在-100℃下仍为韧性断裂。

The figure shows the morphology of tensile port at low temperature of DZ2 (0.05V0Nb) steel at different temperatures. It can be seen from the figure that the fracture tearing edge of DZ2 (0.05V0Nb) steel decreases with the decrease of the test temperature. When the temperature is lower than -60℃, the deep crack begins to appear. There are a lot of dimples on the fracture, indicating that the fracture is still ductile fracture at -100℃.