氢化物对N18锆合金原位拉伸断裂行为的影响

Effects of Hydrides on Fracture Behavior of N18 Zirconium Alloy during in situ Tension

对电解渗氢后的N18锆合金进行了扫描电镜下原位拉伸试验,观察了裂纹在氢化物中的萌发与扩展过程,研究了氢化物对拉伸性能和断裂行为的影响。研究发现,拉伸时试样会发生颈缩,基体断口上存在大量韧窝,呈韧性断裂,使渗氢后的N18锆合金具有一定的塑性。小裂纹在带状氢化物簇中萌发并迅速扩展,但基体对小裂纹的扩展有钝化作用,使小裂纹转化成孔洞。断口表面上,脆性氢化物与基体之间还会形成二次裂纹,其形状和分布与氢化物的形状和分布相似。孔洞与二次裂纹都会使含氢锆合金的塑性降低。

By in situ tension for the N18 zircaloy, which had been charged hydrogen by an electrolytic hydrogenation method, the initiating and developing of cracks inside hydrides were observed with SEM. The effects of hydrides on the tensile properties and the fracture behaviors were investigated. The results show that necking in tension occurs, and many dimples exist on the matrix fracture surface, which means that ductile fracture happens during in situ tension, and that the N18 zircaloy has ductility. The cracks are naturally initiated from strip hydrides clusters and propagate rapidly inside hydrides, but are blunted by plastic matrix, and become to holes. There are many secondary cracks between matrix and brittle hydrides on the fracture surface. Both the shape and distribu tion of the secondary cracks are similar to those of hydrides. The holes and secondary cracks reduce the ductility of the N18 zircaloy with hydrogen.