新锆合金碘致应力腐蚀断口研究

利用扫描电镜和EDXA对新锆合金碘致应力腐蚀的断口进行了形貌观察和成分分析。在断口表面发现腐蚀产物、二次裂纹、沿晶开裂和穿晶准解理开裂等应力腐蚀断裂特征,并观察到锆合金碘致应力腐蚀的“沟槽”特征。起裂区为沿晶开裂,在裂纹扩展阶段,开裂以穿晶为主。断口上腐蚀产物的成分主要是氧和锆,局部准解理开裂区域可检测到碘。去应力退火试样上发现了平行轧面的深沟,且沿晶开裂不明显。试验温度升高,断口上的腐蚀产物增多,而且沿晶开裂更容易。碘分压不仅影响腐蚀产物层的厚度,而且碘分压较高时沿晶开裂容易发生。

A Study on the Fractures of Iodine InducedStress Corrosion Cracking of New Zirconium Alloys (In Chinese)

The morphology and chemical compositions of I-SCC fractures of new zirconium alloys were investigated by SEM and EDXA.The feature on fracture surface for I-SCC samples,such as corrosion products,the secondary cracking,intergranular cracking and pseudo-cleavage transgranular cracking,have been observed.And the fluting,the typical characteristic of I-SCC also has been found.Intergranular cracking is visible at crack initiation stage and transgranular cracking is distinguished at crack propagation stage.The corrosion products are mainly composed of Zr and O;and I can be detected on the local pseudo-cleavage zone.The most of grooves on the fractures of relieved-stress annealing samples are parallel with the roll plane.The intergranular cracking in relieved-stress annealing samples is not obvious.When the test temperature increases,the activity of iodine increases and the stress on crack tip is easier to be released,thus the corrosion products on fracture also increase and intergranular cracking is visible.The partial pressure of iodine influents the thickness of corrosion products,and intergranular cracking is easier to be found when iodine partial pressure is high enough.