Phase Transformations upon Ageing in Ti15Mo Alloy Subjected to Two Different Deformation Methods

Autor: Kristína Bartha, Josef Stráský, Anna Veverková, Jozef Veselý, Jakub Čížek, Jaroslav Málek, Veronika Polyakova, Irina Semenova, Miloš Janeček
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Metals, Vol 11, Iss 8, p 1230 (2021)
Druh dokumentu: article
ISSN: 2075-4701
DOI: 10.3390/met11081230
Popis: Ti15Mo alloy was subjected to two techniques of intensive plastic deformation, namely high pressure torsion and rotary swaging at room temperature. The imposed strain resulted in the formation of an ultrafine-grained structure in both deformed conditions. Detailed inspection of the microstructure revealed the presence of grains with a size of around 100 nm in both conditions. The microstructure after rotary swaging also contained elongated grains with a length up to 1 µm. Isothermal ageing at 400 °C and 500 °C up to 16 h was applied to both conditions to investigate the kinetics of precipitation of the α phase and the recovery of lattice defects. Positron annihilation spectroscopy indicated that the recovery of lattice defects in the β matrix had already occurred at 400 °C and, in terms of positron trapping, was partly compensated by the precipitation of incoherent α particles. At 500 °C the recovery was fully offset by the formation of incoherent α/β interfaces. Contrary to common coarse-grained material, in which the α phase precipitates in the form of lamellae, precipitation of small and equiaxed α particles occurred in the deformed condition. A refined two-phase equiaxed microstructure with α particles and β grain sizes below 1 μm is achievable by simple rotary swaging followed by ageing.
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