| Summary: | This paper presents experimental data on the microstructure and martensite transformation temperatures of Ti<sub>49.8</sub>Ni<sub>50.2</sub> (at%) after <i>abc</i> pressing (multi-axial forging) to different true strains <b><i>e</i></b> from 1.84 to 9.55 at 573 K. The data show that increasing the true strain results in grain–subgrain refinement on different scales at a time. With <b><i>e</i></b> = 9.55 at 573 K, the average grain–subgrain size measured approximately 130 nm. Decreasing the <i>abc</i> pressing temperature from 723 to 573 K caused a decrease in all martensite transformation temperatures, a change in the lattice parameters, R phase formation, and angular shifts of diffraction peaks and their broadening. The largest change in the microstructure of Ti<sub>49.8</sub>Ni<sub>50.2</sub> was provided by <i>abc</i> pressing to <b><i>e</i></b> = 1.84. Increasing the true strain to <b><i>e</i></b> = 9.55 resulted in a much smaller effect, suggesting that the alloy obtained a high density of structural defects even at <b><i>e</i></b> = 1.84. Two possible mechanisms of grain–subgrain refinement are discussed.
|
|---|