The effect of low-temperature strain on the structure and the critical-current degradation of the superconducting alloy Nb-Ti

The structural-phase aspects of the behavior of the critical current under load in the superconductive alloy Nb–48.5 wt% Ti are studied. It is shown that the optimum preliminary strain at T=77 K with subsequent annealing suppresses the tendency of the β matrix of the alloy to undergo phase transformations according to martensitic kinetics under uniaxial tension at T=4.2 K, and this is manifested in the reduction of the critical-current degradation effect when loaded to σ=0.9σfr in a transverse magnetic field of H=5 T. The paper discusses possible critical-current degradation mechanisms under mechanical loading in the niobium-titanium alloy, based on models of critical current flow in the β matrix reinforced with martensitic interlayers.