材料科学
方向错误
晶间腐蚀
晶界
冶金
应力腐蚀开裂
成核
奥氏体不锈钢
焊接
开裂
腐蚀
复合材料
微观结构
热力学
物理
作者
Xiaopeng Xiao,Dianzhong Li,Yiyi Li,Shanping Lu
标识
DOI:10.1016/j.matchar.2021.111309
摘要
Stress relaxation cracking failure is widely reported in the materials used for thermal power plants, which seriously affected the safety of thermal power units under long-term service. In our study, the influence of intergranular precipitation behavior on the stress relaxation cracking susceptibility of Super304H austenitic stainless steel weld metal was investigated based on the pre-compressed CT technique. The 45° misorientation grain boundary has the lowest critical interfacial nucleation energy, followed by the grain boundaries away from the 45° misorientation. As a result, the coarse intergranular M23C6 carbides were more prone to precipitate at 45° misorientation grain boundary, which led to the lowest resistance to stress relaxation cracking susceptibility at 35 to 45° grain boundary. Further analysis indicated that intergranular cavities were easily initiated at the non-coherent M23C6/γ interface. Since the non-coherent interface with a low Cr concentration zone and high specific interfacial energy had a lower strength, the lattice distortion at the non-coherent interface could lead to higher strain concentration.
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