Characterization of aged ω‐phase percipitation in Ti−V (19 at .%) from analysis of rounded superconducting transition calorimetry experiments

The Tc of bcc Ti‐V (19 at .%) obtained by rapid quenching is suppressed by some 2K by a thermal ω‐phase precipitation through the operation of an almost complete proximity effect.1 Subsequent aging at 300°C progressively broadens the transition, decreases its completeness, and increases Tc. These results contrast with equivalent experiments on Ti‐Mo and Ti‐Fe alloys where the transition remains sharp and complete while Tc decreases with aging time. Details of the ω‐phase are quite important, however; the unique phenomenon in the case of Ti‐V (19 at .%) aging data is the occurrence of an incomplete internal proximity effect between the high‐Tc vanadium – rich bcc matrix and large particles of low Tc vanadium – poor ω‐phase. The data analysis2 involves fitting with a BCS model broadened by an asymmetrical Gaussian distribution of Tc’s.