Stable atomic structure of NiTi austenite

Stable atomic structure of NiTi austenite

Nitinol (NiTi), the most widely used shape-memory alloy, exhibits an austenite phase that has yet to be identified. The usually assumed austenitic structure is cubic B2, which has imaginary phonon modes, hence it is unstable. We suggest a stable austenitic structure that " on average " has B2 symmetry (observed by x-ray and neutron diffraction), but it exhibits finite atomic displacements from ...

Shape-memory transformations of NiTi: minimum-energy pathways between austenite, martensites, and kinetically limited intermediate states.

NiTi is the most used shape-memory alloy; nonetheless, a lack of understanding remains regarding the associated structures and transitions, including their barriers. Using a generalized solid-state nudged elastic band method implemented via density-functional theory, we detail the structural transformations in NiTi relevant to shape memory: those between a body-centered orthorhombic (bco) groun...

- Atomic Spectra Atomic Structure

T HE present edition of this work contains a number of corrections and additions; Birge's new set of fundamental constants has been adopted throughout, and various tables, especially the table of ionization potentials, have been brought up to date. The author is indebted to Professor J. W. Ellis of the University of California at Los Angeles for a list of errors and corrections ; several of the...

Research on abnormal grain growth in reversely transformed austenite structure

Site-specific atomic-scale characterisation of retained austenite in a strip cast TRIP steel

Knowledge of carbon content in retained austenite (RA) with different neighbouring phases is essential to understand the chemical stability of RA, which is useful for microstructure tuning of transformation-induced plasticity (TRIP) steels. The present study investigates different morphologies and chemical compositions of RA by correlating electron backscattering diffraction, transmission elect...