In situ neutron diffraction investigation of texture-dependent Shape Memory Effect in a near equiatomic NiTi alloy

Journal article

To explore the possibility of customising the functional behaviour of NiTi shape memory alloy via controlling texture, binary Ni55Ti45 (wt.%) alloys were manufactured in as cast and hot swaged conditions, presenting contrasting initial texture and macroscopic performance. In situ time-of-flight neutron diffraction technique was employed to study the texture effect on the microstructural evolution during Shape Memory Effect (SME), and a range of properties were evaluated. It was found that (i) hot swaging process leads to change in grain morphology and increase in microstrain; (ii) thermal expansion coefficients of martensite and austenite variants were weakly affected by the texture and phase transformation constraint; (iii) significant texture effect on the elastic properties at both macro- and micro-scale was quantified by Elasto-Plastic Self-Consistent (EPSC) modelling approach, while the anisotropic elastic moduli lie within the range for single crystal state and twinned structure; (iv) texture evolution during SME is weakly related to the initial microstructure; (v) grains reoriented so that the <010> axis became aligned parallel to the loading direction, and retained this orientation upon unloading, revealing the underlying correlation between texture evolution and detwinning. Based on the experimental results, a multi-variant model was proposed to quantify the lattice strain evolution during SME. Validity of the conceptually simple and parametrically parsimonious model was confirmed by validation against experimental data.

Authors: Wang, Z; Chen, J; Besnard, C; Kuncicka, L; Kocich, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Acta Materialia
• Volume: 202
• Pages: 135-148
• Publication date: 2020-10-27
• Acceptance date: 2020-10-21
• DOI: 10.1016/j.actamat.2020.10.049
• ISSN: 1359-6454
• Language: English
• Keywords: FFR; texture; in situ neutron diffraction; Shape Memory Effect; EPSC; bespoke NiTi shape memory alloys