Enhancement of irreversibility field and critical current density of rare earth containing V 0.60 Ti 0.40 alloy superconductor by cold-working and annealing

β -V 1−x Ti 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−x Ti x alloys have shown limited success. Improving J C requires a controlled generation of defects. Similar to the V 0.6 Ti 0.4 -RE (RE = Gd, Y) alloys, RE = Ce, Dy and Nd are also immiscible in the V 0.6 Ti 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 0.6 Ti 0.4 -Gd alloy is observed to be significantly lower than that of V 0.6 Ti 0.4 alloy. Cold-working is found to further improve the T C, H C2, H Irr, and J C of all the V 0.6 Ti 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 0.6 Ti 0.4 -RE (RE = Gd, Ce) alloys. The tensile strength is also found to increase to about 60–70% of the V 0.6 Ti 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 0.6 Ti 0.4 -RE alloys. Cold-working on the V 0.6 Ti 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 0.6 Ti 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.