2024/06/18 by Himanshu Vashishtha, Vashishtha, Himanshu, David M. Collins +1
Materials Science · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Shape Memory Alloy Transformations
paper · pdf · doi:10.48550/arxiv.2406.12431
openalex publication_date 2024/06/18 · openalex created_date 2024/06/20 · openalex updated_date 2026/07/28
The ability to control the stress-induced phase transformation of the shape memory alloy, NiTi, is an important technological challenge that must be understood for their wide application in devices that can exploit their reversible strain properties. This study elucidates the direct relationship between dislocation density and the R-phase transformation, including its formation temperature from interrupted annealing of rolled NiTi samples. Deformation is shown to determine the enthalpy change required for the B2→R-phase transformation, with associated transformation temperatures being modifiable via dislocation density and recovery processes. Recovery is shown to be rapid, highly heterogeneous and sensitive to crystal orientation. Grains with a ⟨100⟩ direction close to the macroscopic rolling direction recover more rapidly than ⟨110⟩ and ⟨111⟩ orientated grains. Considered to be governed by processing induced residual stresses and resultant crystallographic dependent annihilation/slip pathways, there are opportunities to tune B2→R-phase transformation on either a grain-averaged or an orientation dependant per-grain basis.