Restriction of grain growth of nano-crystalline Ni-Zr alloy by Zr atoms segregated at grain boundary under high temperature intermittent stressing

摘要

Molecular dynamics (MD) analysis of high-temperature deformation behaviour of nano crystalline (NC) Ni and Ni-Zr alloy (3 at and 6 at Zr segregated along the grain boundaries (GBs)) having grain size similar to 6 nm subjected to intermittent stressing has been carried out employing Embedded atom potential. The creep deformation is intensified during the interrupted creep (IC) test as Zr content increases in NC Ni along the GBs and Zr segregation is also found to restrict the grain growth. The creep rate for IC tests is also increased in case of Ni-Zr alloy as compared to NC Ni and the same also found to be increased with decreasing time interval between the stress interruptions. NC Ni transforms to tri-crystal Ni when subjected to interrupted stressing whereas NC Ni-Zr retains its NC structure throughout the deformation process. It is observed that the GB of the tri-crystal comprises of 2-D HCP structure and dislocation network in case of NC Ni. Addition of Zr along the GBs impedes both dislocation glide and GB movement.