TY - JOUR

T1 - Hydrogen penetration into the NiTi superelastic alloy investigated in-situ by synchrotron diffraction experiments

AU - Weiser, Adam

AU - Todt, Juraj

AU - Holcova, Jitka

AU - Zalezak, Tomas

AU - Paulik, Anna

AU - Holec, David

AU - Jary, Milan

AU - Zobac, Ondrej

AU - Mrazek, Jan

AU - Frenzel, Jan

AU - Keckes, Jozef

AU - Dlouhý, Antonin

PY - 2024/7/23

Y1 - 2024/7/23

N2 - Microstructural changes induced by a hydrogen permeation into the NiTi superelastic alloy were investigated in-situ using the X-ray synchrotron diffraction. A new design of an electrochemical cell enabled to uncover time and position dependent processes under a flat alloy surface exposed to the cathodic hydrogen. The diffraction data supported by thermo-elastic FEM calculations helped to quantify an evolution of compressive stresses in the B2 austenitic phase hosting hydrogen atoms. The compressive stress state initiates a formation of martensitic phases starting from the exposed surface layer and advancing into the alloy volume with increasing time of hydrogen charging. We have performed the ab-initio DFT study in order to rationalize volumetric changes associated with variations in the B2 austenite and B19′ martensite lattice parameters. The numerical results also contributed to the identification of a new hydride phase with orthorhombic crystal structure and lattice parameters a = 0.8505 nm, b = 0.7366 nm and c = 0.4722 nm.

AB - Microstructural changes induced by a hydrogen permeation into the NiTi superelastic alloy were investigated in-situ using the X-ray synchrotron diffraction. A new design of an electrochemical cell enabled to uncover time and position dependent processes under a flat alloy surface exposed to the cathodic hydrogen. The diffraction data supported by thermo-elastic FEM calculations helped to quantify an evolution of compressive stresses in the B2 austenitic phase hosting hydrogen atoms. The compressive stress state initiates a formation of martensitic phases starting from the exposed surface layer and advancing into the alloy volume with increasing time of hydrogen charging. We have performed the ab-initio DFT study in order to rationalize volumetric changes associated with variations in the B2 austenite and B19′ martensite lattice parameters. The numerical results also contributed to the identification of a new hydride phase with orthorhombic crystal structure and lattice parameters a = 0.8505 nm, b = 0.7366 nm and c = 0.4722 nm.

U2 - 10.1016/j.actamat.2024.120217

DO - 10.1016/j.actamat.2024.120217

M3 - Article

VL - 277.2024

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 15 September

M1 - 120217

ER -