The dislocation density in strain-hardened Alloy 690 was analyzed using scanning transmission electron microscopy (STEM) to study the relationship between the local plastic strain and susceptibility to primary water stress corrosion cracking (PWSCC) in nuclear power plants. The test material was cold-rolled at various thickness reduction ratios from 10% to 40% to simulate the strain-hardening condition of plant components. The dislocation densities were measured at grain boundaries (GB) and in grain interiors of strain-hardened specimens from STEM images. The dislocation density in the grain interior monotonically increased as the strain-hardening proceeded, while the dislocation density at the GB increased with strain-hardening up to 20% but slightly decreases upon further deformation to 40%. The decreased dislocation density at the GB was attributed to the formation of deformation twins. After the PWSCC growth test of strain-hardened Alloy 690, the fraction of intergranular (IG) fracture was obtained from fractography. In contrast to the change in the dislocation density with strain-hardening, the fraction of IG fracture increased remarkably when strain-hardened over 20%. From the results, it was suggested that the PWSCC growth behavior of strain-hardened Alloy 690 not only depends on the dislocation density, but also on the microstructural defects at the GB.

使用扫描透射电子显微镜 (STEM) 分析应变硬化合金 690 中的位错密度，以研究局部塑性应变与核电厂初级水应力腐蚀开裂 (PWSCC) 敏感性之间的关系。试验材料以 10% 到 40% 的各种厚度压下率进行冷轧，以模拟植物部件的应变硬化条件。位错密度是在晶粒边界 (GB) 和 STEM 图像应变硬化试样的晶粒内部测量的。随着应变硬化的进行，晶粒内部的位错密度单调增加，而GB处的位错密度随着应变硬化的增加而增加至20％，但在进一步变形至40％时略有下降。GB 位错密度的降低归因于变形孪晶的形成。在应变硬化合金 690 的 PWSCC 生长测试之后，从断口法中获得了晶间 (IG) 断裂的分数。与应变硬化引起的位错密度变化相反，当应变硬化超过 20% 时，IG 断裂的比例显着增加。结果表明，应变硬化合金 690 的 PWSCC 生长行为不仅取决于位错密度，还取决于 GB 处的微观结构缺陷。当应变硬化超过 20% 时，IG 断裂的比例显着增加。结果表明，应变硬化合金 690 的 PWSCC 生长行为不仅取决于位错密度，还取决于 GB 处的微观结构缺陷。当应变硬化超过 20% 时，IG 断裂的比例显着增加。结果表明，应变硬化合金 690 的 PWSCC 生长行为不仅取决于位错密度，还取决于 GB 处的微观结构缺陷。