Cube textured nickel alloy tapes

Cube textured nickel alloy tapes prepared by cold rolling and annealing (RABiTS method) represent a standard metallic substrate for superconductor coatings of the YBa2Cu3O7_d (YBCO) type. These tapes have a width to thickness ratio of about 30–100. However, a value of close to one is optimal concerning low energetic losses under alternating current applications. First experiments on micro-alloyed nickel prove that the cube texture as a typical sheet texture can also be formed in profile wires with a rectangular cross-section after cold drawing and recrystallization treatment.

The experiments were performed on nickel of 99.98at% purity micro-alloyed with 0.033at% yttrium (Ni + 0.033at%Y). This material was chosen because of its excellent cube texture under the conditions of tape preparation and because of its relatively low strength under conditions of heavy cold working.

An Ni + 0.033at%Y ingot of about 32 mm in diameter and 300 mm in length was produced. The ingot was hot rolled at 850 _C to (22 _ 22) mm2 and milled to (20 _ 20) mm2. This metallic rod was cold rolled to a 1 mm thick strip. The edges were wet ground to get strips of 25 mm width and 1 mm thickness. These strips were recrystallized at 300 _C for 15 min and subsequently cold drawn. In this process the (25 _ 1) mm2 strips were drawn through rectangular drawing dies via 15 drafts down to a profile wire with a cross sectional area of (1 _ 1) mm2.

First experiments to develop a cube textured Ni + 0.033at%Y profile wire have shown that a specific drawing process is suitable to achieve a fraction of cube oriented grains in the central region of the recrystallized wires of up to 96.2% within <14.5_ deviation. Further, a fraction of low angle grain boundaries of up to 70.1% within <10.5_ deviation was determined in the wires. Although these characteristics are not sufficient to accomplish the requirements to a cube textured substrate material, they are promising for forthcoming investigations.

Source: J. Eickemeyer, A. Guth, J. Freudenberger, B. Holzapfel, L. Schultz. First steps towards cube textured nickel profile wires for YBCO-coated conductors. Physica C 471 (2011) 549–552.