Relation between negative temperature coefficient in electrical resistivity and athermal ω phase in Ti–xNb (26 ≤ x ≤ 29 at.%) alloys

We have investigated the relation between the negative temperature coefficient (NTC) in electrical resistivity and the formation of the athermal ω phase in Ti–xNb (26 ≤ x ≤ 29 at.%) alloys. The alloys with 26 ≤ x ≤ 28 exhibit NTC in electrical resistivity and a temperature hysteresis appears in the temperature region of NTC. In these alloys, athermal ω phase forms in the temperature range of NTC in resistivity. The alloy with x = 29 also shows NTC but no detectable temperature hysteresis appears. In this alloy, the athermal ω phase does not form, but diffuse satellites appear at gβ+1/2 ζ ζ¯ 0∗, where gβ is a reciprocal lattice vector of the β phase in the temperature range of NTC. These results suggest that NTC in the electrical resistivity in Ti–x  Nb alloys is related not only to the formation of the athermal ω phase but also to the appearance of diffuse satellites at gβ+1/2 ζ ζ¯ 0∗.

► We have investigated the relation between the negative temperature coefficient (NTC) in electrical resistivity and the formation of the athermal ω phase in Ti–xNb (26 ≤ x ≤ 29 at.%) alloys. ► The resistivity of the alloy with x = 26, 27 and 28 exhibit NTC and temperature hysteresis between cooling and heating processes. On the other hand, the resistivity of the alloy with x = 29 shows NTC with no temperature hysteresis. ► Although ω phase forms in the alloy with x = 28, it does not form in the alloy with x = 29. In the latter alloy, diffuse satellites at gβ+1/2 ζ ζ¯ 0∗ appear below Tmin when the zone axis is [1 1 1]. ► We concluded that the NTC in electrical resistivity is related not only to the formation of the athermal ω phase but also to the appearance of a state with exhibiting diffuse satellites at gβ+1/2 ζ ζ¯ 0∗.