Fernando Gustavo Warchomicka

arXiv2025

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

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

cond-mat.mtrl-sci↗

arXiv2024

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

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.

cond-mat.mtrl-sci↗