High sensitivity of the superconducting transition temperature of heterophase titanium alloys to the rate of cooling

A strong influence of the cooling rate, T˙, of specimens on the transition temperature Tc and its kinetics has been found in measuring the superconducting transition in two-phase (α + β) titanium alloys of the Ti–Al–V system. Under standard (slow) cooling conditions, Tc in these alloys varies between 5.7 and 7.0 °K depending on the vanadium concentration. The maximum effect was obtained for T˙ about 10 °K-sec−1, when an unstable and irreversible N–S transition was recorded with Tc = 36 °K and a start of the transition at 42 °K. It is proposed that so great a shift in Tc towards higher temperatures for fairly rapid cooling of the specimen is a consequence of thermoelastic strains arising in it, initiating lattice instability in the vicinity of the structural phase transition in the superconducting β phase.

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