Development of high strength and strongly cube textured Ni-4.5% W/Ni-15% Cr composite substrate for coated conductor application

Abstract

The development of thin, mechanically stronger and highly cube textured substrates is of great technological importance for increasing the engineering current density of the coated conductors. Nickel is a suitable substrate for this in view of its ability to form strong cube texture after heavy rolling and annealing and its excellent oxidation resistance. However, nickel is very soft (yield strength ~40 MPa) and this limits the processing to thin tapes. The ferromagnetism of Ni is also undesirable for ac application of coated conductors in magnetic fields. In the present paper we report on the development of Ni-4.5 at.% W/Ni-15 at.% Cr composite substrates of 80 and 40 μm thickness with strong cube texture, high yield strength (~200 MPa) and reduced magnetisation losses. The strong cube texture was obtained through an optimised two-step recrystallisation annealing following heavy cold working. It was found that the presence of non-cube texture forming alloy (Ni-15% Cr) in the inner core of the composite had no adverse affect on the growth of cube textured grains on the surface (Ni-4.5% W) even at a low substrate thickness of 40 μm. A significant improvement in the texture/misorientation distribution was observed in the CeO 2 buffer layer deposited on the composite substrate.