Dislocation core effects on slip response of NiTi- a key to understanding shape memory. (October 2017)

• Record Type: Journal Article
• Authors: Alkan, S.; Sehitoglu, H.
• Is Part Of: International journal of plasticity. Volume 97(2017:Oct.)
• Page Start: 126
• Page End: 144
• Publication Date: 2017-10
• Subjects: Plasticity -- Periodicals; Plasticité -- Périodiques; Plasticity; Periodicals; 620.11233
• DOI: 10.1016/j.ijplas.2017.05.012
• Languages: English
• ISSNs: 0749-6419

Abstract

Abstract: The understanding of the non-Schmid behavior in shape memory alloy NiTi is considered a significant breakthrough because this alloy still remains enigmatic. We utilize an Eshelby-Stroh formalism in conjunction with Molecular Statics-Peierls stress calculation to predict the experimental CRSS results for three different crystal orientations and tension-compression cases. These combination of tools incorporating elastic anisotropy and core displacements are necessary to develop a precise understanding of non-Schmid behavior. We note the different extents of core spreading produce a highly asymmetric tension-compression behavior and strong orientation dependence governed by the non-glide shear and normal stress components. The experimental results and empiricism free modeling produces excellent agreement, and most importantly enlisting scientific insight into the shape memory response. Graphical abstract: Highlights: A theory is proposed for the slip resistance of B2 NiTi predicting tension-compression asymmetry & orientation dependence. Core spreading is established by continuum-atomistic simulations, and is shown to be responsible for the non-Schmid behaviour. A yield criterion is established for the onset of slip in B2 NiTi. This criterion is in very good agreement with experiments.