Nanoscale phase transition behavior of shape memory alloys — closed form solution of 1D effective modelling. (January 2018)

• Record Type: Journal Article
• Authors: Li, M.P.; Sun, Q.P.
• Is Part Of: Journal of the mechanics and physics of solids. Volume 110(2018)
• Page Start: 21
• Page End: 37
• Publication Date: 2018-01
• Subjects: Grain size effects -- Nanoscale phase transition -- Internal length scales -- Energy dissipation -- Two-phase coexistence; Mechanics, Applied -- Periodicals; Solids -- Periodicals; Mechanics -- Periodicals; Mécanique appliquée -- Périodiques; Solides -- Périodiques; Mechanics, Applied; Solids; Periodicals; 531.05
• DOI: 10.1016/j.jmps.2017.09.008
• Languages: English
• ISSNs: 0022-5096

Abstract

Abstract: We investigate the roles of grain size ( lg ) and grain boundary thickness ( lb ) on the stress-induced phase transition (PT) behaviors of nanocrystalline shape memory alloys (SMAs) by using a Core-shell type "crystallite-amorphous composite" model. A non-dimensionalized length scale l ¯ g ( = l g / l b ) is identified as the governing parameter which is indicative of the energy competition between the crystallite and the grain boundary. Closed form analytical solutions of a reduced effective 1D model with embedded microstructure length scales of lg and lb are presented in this paper. It is shown that, with l ¯ g reduction, the energy of the elastic non-transformable grain boundary will gradually become dominant in the phase transition process, and eventually bring fundamental changes of the deformation behaviors: breakdown of two-phase coexistence and vanishing of superelastic hysteresis. The predictions are supported by experimental data of nanocrystalline NiTi SMAs.