Critical current and flux pinning properties of the superconducting Ti–V alloys

• We have studied the critical current and flux-line pinning force in Ti–V alloys.
• Grain boundaries are found to be the strongest flux-pinners in the Ti–V alloys.
• However, the grain boundaries become less effective in the high field regime.
• Dislocations and ω phase (point-pinners) are effective in the high field regime.
• The flux line lattice has more shear strength in the presence of dislocations.

We present a study on the critical current density and the flux-line pinning properties of a series of annealed and as cast samples of Ti100−xVx (x = 20, 30, 40 and 60) alloys, performed with the help of magnetization measurements. We show that the grain boundaries are the dominant flux pinning centers in the Ti–V alloys in the low and intermediate magnetic field regime. In the high magnetic field regime, the dislocation networks and the point pinning mechanism provided by the ω phase present in these alloys are more effective than the grain boundaries. While in the low magnetic fields we find the signature of surface effects enhancing the pinning force density, a peak effect in the critical current is observed in these alloys in the high field regime near the upper critical field HC2. Using the existing theories we provide an analysis of the pinning force density over a large range of magnetic fields, and obtain some new insight on the influence of various metallurgical phases, grain boundaries and dislocation networks on the flux-line pinning properties of these alloys.