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1. Stress-induced phase transformations in Ti-15Mo alloy at elevated temperature

Author

Harcuba, Petr, Krajňák, Tomáš, Preisler, Dalibor, Kozlík, Jiří, Stráský, Josef, Šmilauerová, Jana, Warchomicka, Fernando Gustavo, and Janeček, Miloš

Subjects
Condensed Matter - Materials Science
Abstract

Controlled mechanical loading was applied to Ti-15Mo alloy during annealing at 550 {\deg}C. Massive formation of the $\omega_{\textrm{iso}}$ phase from the parent $\beta$-phase occurred during annealing at 550 {\deg}C without external stress or with stress well below the yield stress. Moreover, a massive $\alpha$ phase precipitation takes place under simultaneous annealing and plastic deformation. Plastic deformation plays a key role in $\beta\rightarrow\alpha$ transformation and achieving refined $\alpha+\beta$ type microstructure resulted in improved mechanical properties. Studying phase transformations during plastic deformation is critical for understanding and optimizing thermomechanical processing of metastable $\beta$-Ti alloys.

Published
2025

2. Heterogeneous dynamic restoration of Ti-15Mo alloy during hot compression

Author

Shahryari, Esmaeil, Poletti, Maria Cecilia, Preisler, Dalibor, Harcuba, Petr, Strasky, Josef, Janecek, Milos, and Warchomicka, Fernando Gustavo

Subjects
Condensed Matter - Materials Science
Abstract

Near-beta titanium alloys have shown low Young's modulus and good strength, making them excellent implant candidates. However, their processing using thermomechanical routes in single phase beta region results in heterogeneous microstructures due to high content alloying elements and consequent slow diffusion-controlled processes such as dynamic recovery. This study investigates the deformation behaviour of a Ti-15Mo alloy through hot compression experiments using a Gleeble 3800 device in the single beta domain at strain rates from 0.01 s-1 to 10 s-1, reaching final strains of 0.50 and 0.85 followed by immediate water quench. The findings show that the material presents a low strain rate sensitivity. The flow curves show significant strain hardening before reaching a steady-state regime, particularly at high strain rates. The strain hardening exponent calculations support the effect of molybdenum on retarding softening mechanisms such as dynamic recovery. Electron backscatter diffraction (EBSD) measurements of deformed samples revealed that dynamic recovery is the primary restoration mechanism, with continuous and geometric dynamic recrystallisation evidence. Due to the slow restoration process, we observe the subgrain formation for different deformation parameters. Therefore, we introduced an EBSD-based method to quantify dynamic recovery and subgrain size. We concluded that dynamic recovery and dynamic recrystallisation decrease as the strain rate increases with minimal variation at higher strain rates., Comment: 21 pages, 12 figures, 61 references, Submitted to Journal of Materials Research and Technology

Published
2024
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3. THE EFFECT OF VARIOUS SILICATE-GLASS MATRIXES ON GOLD-NANOPARTICLE FORMATION

Author

Blanka Svecova, Pavla Nekvindova, Stanek Stanislav, Vytykacova Sona, Mackova Anna, Malinsky Petr, Miksova Romana, Janecek Milos, Pesicka Josef, and Spirkova Jarmila

Subjects
Glasses, Nano particles, Transmission electron microscopy (TEM), Ion implantation, Clay industries. Ceramics. Glass, TP785-869
Abstract

Ion implantation of Au+ with energy of 1.7 MeV and a fluence of 1 x 1016 ions.cm-2 along with post-implantation annealing were used to synthesize metal nanoparticles in various types of silicate glasses. The objective of the work was the investigation of the effect of the host glass matrix on the principle properties of the nanoparticles. The prepared samples were characterized in terms of their chemical composition and the nucleation of gold nanoparticles. The largest nanoparticles having a radius of 1-25 nm and an irregular shape were detected in the glass BK7 containing boron trioxide in its structure. On the other hand, small nanoparticles (1-5 nm) with a spherical shape were found in glass with a structure similar to silica. The shape, size and distribution of the nanoparticles are strongly influenced by the divergence of the annealing temperature from the transformation temperature of the particular glass

Published
2016
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9. Single crystal growth of TIMETAL LCB titanium alloy by a floating zone method

Author

Šmilauerová, Jana, Pospíšil, Jiří, Harcuba, Petr, Holý, Václav, and Janeček, Miloš

Subjects
Condensed Matter - Materials Science
Abstract

The methodology of single crystal growth of metastable $\beta$-Ti alloy TIMETAL LCB in an optical floating zone furnace is presented in this paper. Chemical compositions of both precursor material and single crystals were checked. It was found that the concentration of base alloying elements did not change significantly during the growth process, while the concentrations of interstitial elements O and N increased. DSC measurement determined that this concentration shift has a slight impact on ongoing phase transformations, as in the single-crystalline material peak associated with $\alpha$ phase precipitation moves by a few degrees to a lower temperature and peak attributed to diffusion controlled growth of $\omega$ particles shifts to a higher temperature. X-ray reciprocal space maps were measured and their simulation showed that the single crystal has a mosaic structure with mean size of mosaic blocks of approximately 60 nm.

Published
2018
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10. Ordered array of $\omega$ particles in $\beta$-Ti matrix studied by small-angle X-ray scattering

Author

Šmilauerová, Jana, Harcuba, Petr, Stráský, Josef, Stráská, Jitka, Janeček, Miloš, Pospíšil, Jiří, Kužel, Radomír, Brunátová, Tereza, Holý, Václav, and Ilavský, Jan

Subjects
Condensed Matter - Materials Science
Abstract

Nanosized particles of $\omega$ phase in a $\beta$-Ti alloy were investigated by small-angle X-ray scattering using synchrotron radiation. We demonstrated that the particles are spontaneously weakly ordered in a three-dimensional cubic array along the $\langle 100\rangle$-directions in the $\beta$-Ti matrix. The small-angle scattering data fit well to a three-dimensional short-range-order model; from the fit we determined the evolution of the mean particle size and mean distance between particles during ageing. The self-ordering of the particles is explained by elastic interaction between the particles, since the relative positions of the particles coincide with local minima of the interaction energy. We performed numerical Monte Carlo simulation of the particle ordering and we obtained a good agreement with the experimental data.

Published
2018
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