Effect of Microstructure on Superconducting Properties of Mo/34 at.% Re Alloy

The effect of deformation and heat-treatments on magnetisation of superconducting Mo/34 at. % Re alloy was investigated. The microstructure was studied using optical and electron microscopy. The values of the parameter kappa of the GLAG theory were determined by using three different methods, and they are found to be in accordance with some of the predictions of the Maki theory. The results show that in deformed specimens the magnetic hysteresis is mainly due to the interaction of Abrikosov supercurrent vortices with dislocation tangles; both twin boundaries and grain boundaries are relatively ineffective in causing flux hindrance. The hysteresis observed after annealing has been explained in terms of the occurrence of dislocation rearrangement and the precipitation of the sigma phase. Flux-pinning by dislocation tangles has been treated as a special case of pinning by normal particles and a magnitude of the resulting pinning force is obtained. The experimental results are compared with the predictions of a theoretical model of flux-pinning.