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The mechanism responsible for high critical current densities in Nb-60 at % Ti alloy, one of the most widely used superconductors, has been studied. The critical currents are measured as a function of magnetic field at temperatures between 4.2K and the transition temperature. Specimens, in the shape of copper clad wires of 0.25 mm in diameter, have been heavily cold worked and annealed for various time intervals at 350 C=400 C. The results of measurements show that the dislocation is rearranged in an early stage of annealing and that the precipitates on the dislocation network play an important role in enhancement of critical currents. The pinning force density obeys a scaling rule of the form Fp=(Hc2(T))5/2f(B/Hc2) as predicted upon recent theories.