A508-3钢质子辐照条件下微结构演变研究

STUDY ON THE MICROSTRUCTURE EVOLUTION OF A508-3 STEEL UNDER PROTON IRRADIARION

在室温下利用190 keV质子对A508-3钢进行辐照,辐照剂量分别为0.108,0.216和0.271 dpa.对辐照前后样品的微结构进行了TEM观察.结果表明,辐照没有产生可观察到的微空洞,辐照缺陷主要是位错环,且大部分为Burgers矢量为〈100〉型的间隙型位错环;位错环大部分均匀分布在基体内,还可见位错环分布在位错线附近的情况;随辐照剂量的增加,位错环尺寸分布范围变宽,平均直径增大,当辐照剂量从0.108 dpa增至0.271 dpa时,位错环的平均直径由约1.8 nm增至约4.6 nm;位错环的数量密度在10^(22)m^(-3)数量级并随辐照剂量增加略有增加.对位错环的形成机制及辐照剂量对辐照硬化和脆化程度的影响进行了分析.在实验范围内,由位错环引起的硬化和脆化程度随辐照剂量增加而增大,未出现饱和现象.

Irradiation embrittlement of reactor pressure vessel （RPV） steels is one of critical issues for integrity and safety in long-life operation of light water reactors. The the embrittlement is attributed to three main nano-scale microstructural features including copper rich precipitates, matrix damage and grain boundary segregation. The relevance of matrix component of damage can be high in low copper content alloys and also in the case of high doses. Some recent works have been done in trying to clarify the exact nature of this component of the damage in irradiated commercial steels. This is still an open question： how the irradiation-induced microstructure will evolve in the A508-3 steel in the high dose range. In the present work, in order to emulate the neutron irradiation damage in the RPV steels, 190 keV proton irradiations were conducted on a A508-3 steel to 0.108, 0.216 and 0.271 dpa at room temperature. The irradiation-induced microstructure was examined by TEM. The obtained results show that the irradiation-induced defects are mainly dislocation loops, majority of which are both of （100/ type and of interstitial type, without the observation of the micro-voids. Dislocation loops distribute roughly evenly in the matrix, and some dislocation loops decorate the pre-existing dislocation lines.As the irradiation dose increase, the average diameter of dislocation loops increase and the size distri- bution of dislocation loops become broader. As the dose increased from 0.108 dpa to 0.216 dpa and 0.271 dpa, the average diameter of loops increase from about 1.8 nm to about 3.0 and about 4.6 nm, the number density of loops are in the order of 10^22 m-3 with an weak increasing trend. The formation mechanism of dislocation loops and the effect of dose on hardening and embrittlement were discussed. Irradiation-induced dislocation loops cause hardening and embrittlement in the A508 3 steel, which would not saturate at the studied dose range. The dose dependence of yield strength increment and transition temperature shift follows a power law.