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.
