Irradiation Induced Grain Boundary FlowA New Creep Mechanism at the Nanoscale

• Published in: Nano letters 2012-08, Vol.12 (8), p.4084-4089
• Main Authors: Ashkenazy, Yinon, Averback, Robert S
• Format: Article
• Language: English
• Subjects: Amorphous materials; Condensed matter: structure, mechanical and thermal properties; Creep (materials); Creep rate; Exact sciences and technology; Grain boundaries; Irradiation; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Molecular dynamics; Nanocrystalline materials; Nanocrystals; Nanostructure; Physics; Point defects; Radiation effects on specific materials; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl301554k

A new mechanism of irradiation enhanced creep is proposed for nanocrystalline materials. It derives from local relaxations within the grain boundaries as they absorb point defects produced by irradiation. The process is studied by inserting point defects into the grain boundaries and following the materials response by molecular dynamics. Calculated creep compliances are found in good agreement with those measured in dilute nanocrystalline Cu–W alloys [Tai, K.; Averback, R. S.; Bellon, P.; Ashkenazy Y. Scr. Mater. 2011, 65, 163]. The simulations provide a direct link between irradiation induced creep in nanocrystalline materials with radiation-induced viscous flow in amorphous materials, suggesting that grain boundaries in these materials can be treated as an amorphous phase. We provide a simple analytic model based on this assumption that reproduces the main features of the observed creep rates, a linear dependence on stress, inverse dependence of grain size, a weak dependence on temperature, and a reasonable estimate of the absolute creep rate.