Novel precipitate structures in alloys under irradiation

self-organization;irradiation

Shu, Shipeng

关键词: self-organization;    irradiation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/88942/SHU-DISSERTATION-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

We investigate the fundamentals of precipitate stability under energetic particle irradiation, towards the goal of better controlling the microstructures of driven alloys. First we focus on an irradiation-induced precipitatewithin- precipitate structure, which is referred to as “cherry-pit” structure. We show by computer simulation and analytical modeling that the formation of cherry-pit structure is a special instance of compositional patterning, and that the conditions for compositional patterning and the formation of cherry-pit structures are related, but different from each other. Then we develop a new kinetic Monte Carlo model, which includes the generation, recombination, and sink elimination of irradiation-induced point defects, as well as ballistic mixing. With this tool we explore the possibility of using point-defect sinks to alter the temperature range where compositional patterns are stable. This novel approach for optimizing radiation-resistant materials is then tested experimentally using a Cu-Ag-W model alloy. Lastly we show that the addition of a high density of W nanoparticles dramatically alters the coarsening behavior of precipitate-hardened Cu-Ag alloys. First, the nanoparticles suppress precipitate growth, but far more surprisingly they induce non-equilibrium Ag wetting layers on grain boundaries. This observation is explained using kinetic Monte Carlo simulations, which show that caging of Ag precipitates by the W nanoparticles suppresses their growth and drives the formation of the wetting layers.