Phase Transformations in Ti-15Mo Investigated by in situ Electrical Resistance

P. Zháňal, P. Harcuba, J. Šmilauerová, J. Stráský, M. Janeček, B. Smola, M. Hájek Department of Physics of Materials, Charles University in Prague, Prague, Czech Republic

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In this study phase transformations in metastable beta Ti-15Mo alloy were investigated by an in situ electrical resistance measurement in a wide range of temperatures from -196°C to 850°C. Different temperature ranges of the evolution of electrical resistance were correlated with underlying phase transformations. In the low temperature range, stage I (from -196°C to 220°C) the decrease of electrical resistance with increasing temperature is caused by the dissolution of ω ath (formed during quenching by athermal shuffle transformation) which is accompanied by the relaxation of lattice strain, while the diffusional assisted growth of ω iso in the range from 220°C to 380°C (stage II) is the main mechanism causing the increase of resistance. Another decrease of the resistance in the range from 380°C to 550°C (stage III) is explained by the dissolution or transformation of ωiso. The increase of resistance above 550°C (stage IV) is related to the growth of α-phase particles. The fully reversible character of ωath growth and dissolution during heating and cooling in the stage I up to 100°C was confirmed by temperature cycling during repeated in situ resistance runs from RT. Pre-ageing of samples at 300°C promotes the formation of ωiso particles. Subsequently, ωath particles are not created, which is fully consistent with electrical resistance measurements. The presence of ωath and the orientation relationship between ω and β were identified by the electron diffraction.

DOI: 10.12693/APhysPolA.128.779 PACS numbers: 64.70.kd