Shin-ya Komatsu1, Masahiko Ikeda1, Takashi Sugimoto1, Kiyoshi Kamei1 and Kouichiro Inoue2
1Department of Materials Science and Engineering, Faculty of Engineering, Kansai University, Suita
It was investigated whether the negative temperature dependence of resistivity will appear in Ti-Fe alloys of eutectic type, similarly to other β-isomorphous type Ti alloys. With Ti-Fe alloys quenched from 1173 K, X-ray diffraction, optical microscopy, resistivity measurement and hardness test were carried out.
β phase was retained in the alloys containing more than 4%Fe. Reflections or diffuse scattering of ω phase were not obvious in the alloys containing more than 5%Fe.
The negative temperature dependence appeared in the Fe concentration range between 5 and 15%. This anomalous temperature depndence can be interpreted by the reversible formation and disappearance of athermal ω phase with cooling and heating below room temperature, similarly to other β-isomorphous type Ti alloys.
The hardness showed a maximum at 4% and increased again above 10%. This can be explained by the hardening proportional to the amount of the athermal ω phase formed at room temperature and the solution hardening by Fe in the β phase.
As compared with other β-Ti alloys in terms of the electron/atom ratio (e/a), the resistivity at liquid nitrogen temperature of 6%Fe, 1.9 μΩm, was the largest. The decrease of the resistivity, as in the case of the resistivity ratio ρLN/ρRT, beyond a peak with increasing e/a was the least amount in the Ti-Fe alloys. From these observations, the decrease of the starting temperature for formation of the athermal ω phase per unit e/a was considered to be the smallest in Ti-Fe alloys.
titanium-iron alloys, resistivity, temperature dependence, athermal ω phase, retained β phase, content range, hardness
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