Dislocation loop evolution and radiation hardening in nickel-based concentrated solid solution alloys

• Published in: Journal of nuclear materials 2020-09, Vol.538 (C), p.152247, Article 152247
• Main Authors: Xiu, Pengyuan, Osetsky, Yuri N., Jiang, Li, Velisa, Gihan, Tong, Yang, Bei, Hongbin, Weber, William J., Zhang, Yanwen, Wang, Lumin
• Format: Article
• Language: English
• Subjects: Alloys; Chemical composition; Composition effects; Concentrated solid solution alloys; Cyclic loads; Dislocation; Dislocation loop; Dislocation loops; Ion irradiation; Iron compounds; Irradiation; Irradiation effect; Irradiation hardening; MATERIALS SCIENCE; Microstructural evolution; Nanoindentation; Nickel; Nickel base alloys; Nickel compounds; Radiation; Radiation dosage; Radiation hardening; Radiation measurement; Solid solutions; Stiffness; Ternary alloys
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2020.152247

Effects of chemical composition, ion irradiation dose and temperature on unfaulting of irradiation induced Frank dislocation loops to perfect loops in two nickel based single-phase solid solution alloys, Ni–20Fe and NiFe–20Cr, have been studied. The fraction of Frank loops decreases with irradiation dose from 7.2 to 38.4 dpa at 500°C, but with more Frank loops remaining in the ternary alloy. However, perfect loops and dislocation networks become the dominant features of defects at 580°C in both alloys. The results indicate a thermally assisted loop unfaulting process that may be hindered by more sluggish defect motion in the alloy with more chemical components. Nano-indentation with both continuous stiffness method and single indentation method are used to measure radiation hardening. Loop unfaulting in both alloys irradiated at 580°C reduced radiation hardening while significant hardening is observed after irradiation at 500°C. The quasi-static single indentation method exhibits lower hardness results compared to continuous stiffness method, because dislocations induced from the cyclic loading in the latter method get relaxed and stabilized, resulting in higher resistance to the indenter. [Display omitted] •High irradiation dose and temperature favor unfaulting of Frank dislocation loops to perfect loops that can reduce radiation hardening.•The process of loop unfaulting may be hindered by sluggish diffusion in chemically more complex alloy.