Enhancement of irreversibility field and critical current density of rare earth containing V0.60Ti0.40 alloy superconductor by cold-working and annealing

β-V _1−xTi _x alloy superconductors are considered to be promising materials for high magnetic field applications. So far, attempts to improve the critical current density ( J _C) of β-V _1−xTi _x alloys have shown limited success. Improving J _C requires a controlled generation of defects. Similar to the V _0.6Ti _0.4 -RE (RE = Gd, Y) alloys, RE = Ce, Dy and Nd are also immiscible in the V _0.6Ti _0.4 matrix. The superconducting transition temperature ( T _C), upper critical field ( H _C2), irreversibility field ( H _Irr), and J _C increase with the RE addition. However, the tensile strength of V _0.6Ti _0.4-Gd alloy is observed to be significantly lower than that of V _0.6Ti _0.4 alloy. Cold-working is found to further improve the T _C, H _C2, H _Irr, and J _C of all the V _0.6Ti _0.4-RE alloys. Successive cold-working (with 50% reduction of thickness each time) and annealing (SCA) at 450 ^∘C for 5 hrs is found to significantly improve the H _Irr, and J _C of V _0.6Ti _0.4 -RE (RE = Gd, Ce) alloys. The tensile strength is also found to increase to about 60–70% of the V _0.6Ti _0.4 alloy after the third annealing. It is observed that α ′ and ω phases form at the defect sites at various stages of cold-working and annealing. J _C(H = 0) and H _Irr are about 840 Amm ⁻² and 7 T respectively for the as-cast V _0.6Ti _0.4-RE alloys. Cold-working on the V _0.6Ti _0.4-RE alloys further improves the J _C(H = 0) and H _Irr to about 1250 Amm ⁻² and 8.45 T respectively. SCA increases the J _C(H = 0) and H _Irr to about 4000 Amm ⁻² (or more) and 9 T respectively, and the J _C(7 T) to about 500 Amm ⁻² in V _0.6Ti _0.4 -RE alloy at 4 K. We present a detailed description of the defect structure in these alloys and its role in pinning the magnetic flux lines, thereby improving the overall J _C.