Electrical Conductivity (Resistivity) Measurement of ω Titanium

• Published in: MATERIALS TRANSACTIONS Vol. 66; no. 5; pp. 561 - 568
• Main Authors: Masuda, Takahiro, Kitahara, Hiromoto, Mito, Masaki, Nishiyama, Norimasa, Horita, Zenji, Fukunaga, Kosuke, Naragino, Kaishi
• Format: Journal Article
• Language: English
• Published: Sendai The Japan Institute of Metals and Materials 01.05.2025; 公益社団法人 日本金属学会; Japan Science and Technology Agency
• Subjects: allotropic phase transformation; Diamond pyramid hardness; Dislocation density; EBSD; electrical conductivity; Electrical resistivity; Electron back scatter; Grain boundaries; Grain size; Hardness measurement; High pressure; High temperature; high-pressure torsion; Liquid helium; Microstructure; Plastic deformation; pure Ti; severe plastic deformation; Superconducting quantum interference devices; Superconductors; Vickers microhardness
• ISSN: 1345-9678; 1347-5320
• DOI: 10.2320/matertrans.MT-MC2024012

This study presents measurements of electrical conductivity and Vickers microhardness of ω phase in pure Ti. Samples containing 100% ω phase is produced by a high-pressure synthesis under an elevated temperature. The results are compared with those of 100% α phase in an as-received state and of the samples processed by high-pressure torsion (HPT) where severe plastic strain is imposed under a high pressure. For the electrical conductivity measurement, a contactless method using a superconducting quantum interference device magnetometer is employed, which allows the measurement over a wide range of temperature down to the liquid helium temperature. Vickers microhardness measurement is conducted for the ω phase under different applied loads to minimize the effect of reverse transformation from the ω phase to the α phase during the measurement. Microstructures are observed by electron back scatter diffraction analysis, showing that the grain size is of ∼12 µm containing less dislocations, and this structure is in contrast with the HPT-processed sample having high densities of dislocations and grain boundaries. This difference in the microstructure results in appreciably lower electrical conductivity in a temperature range below ∼100 K for the HPT-processed sample. No anomaly of a superconductive signal is detected in the ω phase down to the temperature of 1.8 K, suggesting that a superconductive state does not exist at ambient pressure in the corresponding temperature range.