Comparative creep behaviour study between single crystal Nickel and ultra-fine grained nano crystalline Nickel in presence of porosity at 1120 K temperature

Department of Metallurgical and Materials Engineering, National Institute of Technology Rourkela, Rourkela 769008, Odisha, India
e-mail: pals@nitrkl.ac.in

Received: 18 August 2015
Accepted: 17 October 2016

Abstract

Molecular dynamics (MD) using embedded atom method (EAM) potential has been performed for the simulation of the creep behaviour of virtual single crystal (SC) Ni and nano-crystalline (NC) Ni having grain size ~ 4 nm with and without presence of porosity (porosity ~ 1 at.%). The dependence of the kinetics of creep deformation of SC Ni and NC Ni on atomic configuration is rationalized in this paper. NC Ni exhibits pronounced as well as extensive primary creep and tertiary creep regimes at operating temperature 1120 K. Grain boundary is observed to be broadened during creep process of NC Ni due to resultant diffusion fluxes across the grain boundaries. In addition overall randomness inside the NC Ni sample is found to increase as creep deformation process progress and the NC Ni sample becomes amorphous at tertiary part of creep curve. The MD study reveals that, the negative effect of porosity on creep behaviour of SC Ni is more significant compared to the effect of porosity on creep behaviour of NC Ni. Nano size SC Ni is found to be better creep resistant material in comparison with NC Ni.