High-Field Superconducting Properties of Ti-Mo Alloys

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Abstract
Critical current densities Jc for restoration of detectable resistance have been measured for super‐conducting Ti‐Mo alloys at 1.2°K in steady magnetic fields up to 30 kG, and for approximate Mo concentrations of 6, 9, and 16 at. %. Cold‐rolling is observed to increase the Jc values considerably and, in the case of Ti‐16 at. % Mo, to result in a marked ``anisotropy'' of Jc similar to that observed in many other cold‐rolled alloy superconductors: at high fields Jc is essentially a maximum or minimum when the applied transverse magnetic field (H⊥J) is, respectively, parallel or perpendicular to the rolling plane, apparently independent of specimen geometry. This suggests that Jc is very sensitive to the relative orientation of the field and an anisotropic defect structure normally introduced during cold‐rolling. The Jc anisotropy does not appear to be critically dependent upon the angle between the current and the rolling direction for current directions in the rolling plane and can apparently be suppressed by martensitic transformation during cold‐rolling. Although an explanation of Jc anisotropy in cold‐worked alloys does not fall within the scope of homogeneous alloy‐negative surface energy theories, the ``upper'' resistive critical fields [Hr(J=1A/cm2)] for these alloys, ranging from 26.5 to 64 kG, are in fair agreement with predictions of the Ginzburg‐Landau‐Gor'kov‐Abrikosov theory.