Li Tong, Xie Yaoping, Wang Xiaojiao, Shen Qin, Li Jiabao, Guo Haibo, Xu Jingxiang, Liu Wenqing
Institute of Materials, School of Materials Science and Engineering, Shanghai University Shanghai 200444 China
Shanghai Institute of Ceramics Academy of Science Shanghai 201899 China.
RSC Adv. 2019 Jun 24;9(34):19620-19629. doi: 10.1039/c9ra03226f. eCollection 2019 Jun 19.
Fe-1.0Cu (at%) and Fe-1.2Cu-2.2Mn alloys aged at 450 °C for 0.25 h, 1 h, 2 h, and 16 h after solution treatment at 900 °C for 2 h are investigated to reveal the role of the addition of Mn on the Cu precipitates in Fe-Cu based alloys. Density functional theory (DFT) total energy calculations on point defects and their influence on Cu precipitates are also performed to understand the nucleation and growth of Cu precipitates. Experiments show that addition of Mn can slightly increase the aging peak hardness by 10 HV; by using atom probe tomography (APT) and optical microscopy, we identify that the increase in hardness derives from both grain refinement and the increase of number density of precipitates. DFT calculations show that Mn increases the formation possibility of Frenkel pairs, , atomic vacancy and self-interstitial atoms, and these two types of defects both serve as nucleation sites of Cu precipitates, resulting in the increase of the nucleation centers number density, which is consistent with our APT experiments on the very initial stage of aging. Moreover, calculated results show that Mn increases the density of atomic vacancies and promotes the evolution rate of Cu precipitates, which accounts for our APT experiments where precipitates in Fe-Cu-Mn grow more quickly than in Fe-Cu. Finally, we also discuss the relationship between Mn content in reactor pressure vessel steels and its irradiation damage effects.
研究了在900℃固溶处理2 h后，于450℃时效0.25 h、1 h、2 h和16 h的Fe-1.0Cu（原子百分比）和Fe-1.2Cu-2.2Mn合金，以揭示添加Mn对Fe-Cu基合金中Cu析出相的作用。还进行了关于点缺陷的密度泛函理论（DFT）总能量计算及其对Cu析出相的影响，以了解Cu析出相的形核和生长。实验表明，添加Mn可使时效峰值硬度略有增加，提高10 HV；通过原子探针断层扫描（APT）和光学显微镜，我们确定硬度的增加源于晶粒细化和析出相数量密度的增加。DFT计算表明，Mn增加了弗伦克尔对、原子空位和自间隙原子的形成可能性，这两种类型的缺陷均作为Cu析出相的形核位点，导致形核中心数量密度增加，这与我们在时效初始阶段的APT实验结果一致。此外，计算结果表明，Mn增加了原子空位密度并促进了Cu析出相的析出速率，这解释了我们的APT实验结果，即Fe-Cu-Mn合金中的析出相比Fe-Cu合金中的析出相生长更快。最后，我们还讨论了反应堆压力容器钢中Mn含量与其辐照损伤效应之间的关系。
