Effect of temperature on creep behavior of nanocrystalline Ni having multimodal grain distribution with pre-existing crack

Abstract

The effect of temperature on creep behavior of multimodal distribution in nanocrystalline (NC) Ni with and without internal crack having average grain size of ~ 7 nm has been studied using a molecular dynamic (MD) simulation with an embedded atom method potential. Creep curves for multimodal distribution in NC Ni with and without internal crack are observed to be shifted downward with increasing temperature. Internal crack having crack size 8 nm x 3 nm x 3 nm in ultra-fine grained NC Ni is observed to be closed during creep deformation. A 14 nm x 14 nm x 14 nm cubic box of simulation is taken for carrying out MD simulation which contained 247530 and 254188 atoms for with and without internal crack respectively. Total number of non-uniform grain is 8 contained in the specimen which is randomly orientated. MD simulation of creep for with and without internal crack specimen has been carried out at 1209, 1409, 1509 K temperatures and constant stress of 1.0 GPa. Atomic trajectory analysis, Centro-symmetry parameter analysis, Wigner–Seitz defect analysis, common neighbor analysis, Voronoi cluster analysis and radial distribution function have been carried out to study structural change under creep process. Deviations in number of generated vacancy with increase in creep strain for various temperatures are studied. Variation of crystal structure is also studied under creep process for different temperature and constant stress of 1.0 GPa.