Stress-induced phase transformation and pseudo-elastic/pseudo-plastic recovery inintermetallic Ni–Al nanowires

Abstract

Extensive molecular dynamics (MD) simulations have been performed in a B2-NiAlnanowire using an embedded atom method (EAM) potential. We show a stress induced-centered-tetragonal (BCT) phase transformation and a novel temperature and cross-section dependentpseudo-elastic/pseudo-plastic recovery from such an unstable BCT phase with a recoverable strainof ∼30% as compared to 5–8% in polycrystalline materials. Such a temperature and cross-sectiondependent pseudo-elastic/pseudo-plastic strain recovery can be useful in variousinteresting applications of shape memory and strain sensing in nanoscale devices.Effects of size, temperature, and strain rate on the structural and mechanicalproperties have also been analyzed in detail. For a given size of the nanowirethe yield stress of both the B2 and the BCT phases is found to decrease withincreasing temperature, whereas for a given temperature and strain rate the yieldstress of both the B2 and the BCT phase is found to increase with increase inthe cross-sectional dimensions of the nanowire. A constant elastic modulus of∼80 GPa of the B2 phase is observed in the temperature range of 200–500 K for nanowires ofcross-sectional dimensions in the range of 17.22–28.712 Å, whereas the elastic modulus ofthe BCT phase shows a decreasing trend with an increase in the temperature.