Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy

Dmitry Gunderov; Karina Kim; Sofia Gunderova; Anna Churakova; Yuri Lebedev; Ruslan Nafikov; Mikhail Derkach; Konstantin Lukashevich; Vadim Sheremetyev; Sergey Prokoshkin

doi:10.3390/ma16041754

Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy

Materials (Basel). 2023 Feb 20;16(4):1754. doi: 10.3390/ma16041754.

Authors

Dmitry Gunderov^{1

2}, Karina Kim^{1

2}, Sofia Gunderova^{1

2}, Anna Churakova^{1

2}, Yuri Lebedev², Ruslan Nafikov¹, Mikhail Derkach³, Konstantin Lukashevich³, Vadim Sheremetyev³, Sergey Prokoshkin³

Affiliations

¹ Department of Materials Science and Physics of Metals, Ufa University of Science and Technology, Zaki Validi St. 32, 450076 Ufa, Russia.
² Laboratory of Solid State Physics, Institute of Molecule & Crystal Physics, UFRC RAS, 151 Prospect Oktyabrya, 450075 Ufa, Russia.
³ Metal Forming Department, National University of Science and Technology "MISiS", Leninsky Ave. 4, p. 1., 119049 Moscow, Russia.

Abstract

The Ti-18Zr-15Nb shape memory alloys are a new material for medical implants. The regularities of phase transformations during heating of this alloy in the coarse-grained quenched state and the nanostructured state after high-pressure torsion have been studied. The specimens in quenched state (Q) and HPT state were annealed at 300-550 °C for 0.5, 3, and 12 h. The α-phase formation in Ti-18Zr-15Nb alloy occurs by C-shaped kinetics with a pronounced peak near 400-450 °C for Q state and near 350-450 °C for HPT state, and stops or slows down at higher and lower annealing temperatures. The formation of a nanostructured state in the Ti-18Zr-15Nb alloy as a result of HPT suppresses the β→ω phase transformation during low-temperature annealing (300-350 °C), but activates the β→α phase transformation. In the Q-state the α-phase during annealing at 450-500 °C is formed in the form of plates with a length of tens of microns. The α-phase formed during annealing of nanostructured specimens has the appearance of nanosized particle-grains of predominantly equiaxed shape, distributed between the nanograins of β-phase. The changes in microhardness during annealing of Q-specimens correlate with changes in phase composition during aging.

Keywords: Ti-18Zr-15Nb shape memory alloys; high-pressure torsion; phase transformations during heating.

Grants and funding

The authors appreciate the support of this work by the Russian Science Foundation project No. 20-69-47029. The alloy fabrication was carried out during the implementation of the strategic project, “Biomedical materials and bioengineering”, within the framework of the Strategic Academic Leadership Program “Priority 2030” at NUST «MISiS».