Mullurkara Suraj Venkateshwaran, Bejawada Akshara, Sen Amrita, Sun Cheng, Bachhav Mukesh, Wharry Janelle P
School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USA.
Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, India.
Materials (Basel). 2023 Jul 6;16(13):4852. doi: 10.3390/ma16134852.
Austenitic stainless steel D9 is a candidate for Generation IV nuclear reactor structural materials due to its enhanced irradiation tolerance and high-temperature creep strength compared to conventional 300-series stainless steels. But, like other austenitic steels, D9 is susceptible to irradiation-induced clustering of Ni and Si, the mechanism for which is not well understood. This study utilizes atom probe tomography (APT) to characterize the chemistry and morphology of Ni-Si nanoclusters in D9 following neutron or proton irradiation to doses ranging from 5-9 displacements per atom (dpa) and temperatures ranging from 430-683 °C. Nanoclusters form only after neutron irradiation and exhibit classical coarsening with increasing dose and temperature. The nanoclusters have NiSi stoichiometry in a Ni core-Si shell structure. This core-shell structure provides insight into a potentially unique nucleation and growth mechanism-nanocluster cores may nucleate through local, spinodal-like compositional fluctuations in Ni, with subsequent growth driven by rapid Si diffusion. This study underscores how APT can shed light on an unusual irradiation-induced nanocluster nucleation mechanism active in the ubiquitous class of austenitic stainless steels.
奥氏体不锈钢D9因其与传统300系列不锈钢相比具有更高的抗辐照能力和高温蠕变强度，而成为第四代核反应堆结构材料的候选材料。但是，与其他奥氏体钢一样，D9易受辐照诱导的Ni和Si团簇化影响，其机制尚不清楚。本研究利用原子探针断层扫描（APT）来表征D9在中子或质子辐照后的剂量范围为每原子5-9个位移（dpa）、温度范围为430-683°C时Ni-Si纳米团簇的化学性质和形态。纳米团簇仅在中子辐照后形成，并随着剂量和温度的增加呈现出典型的粗化现象。纳米团簇具有NiSi化学计量比，呈Ni核-Si壳结构。这种核壳结构为一种潜在的独特成核和生长机制提供了见解——纳米团簇核可能通过Ni中局部的、类似旋节线的成分波动成核，随后由快速的Si扩散驱动生长。本研究强调了APT如何能够揭示在普遍存在的奥氏体不锈钢中活跃的一种不寻常的辐照诱导纳米团簇成核机制。
