The Preparation Of Ni-W Alloy Baseband For Coated Conductor Applications And The Control Of Cubic Texture

YBCO high temperature superconducting coated material has prevalent application in electric engineering, transportation, military, energy intelligence and many other fields. The nickel-tungsten(Ni-W) alloy baseband prepared by rolling assisted biaxially textured substrates(RABiTS) technology satisfies the basic requirements of coated conductors. The alloy with5at.%W has already achieved commercial production, however, it can hardly meet the requirements of high performance coating conductor due to its low mechanical performance and large magnetism. Research shows that increasing the proportion of W element improves the mechanical properties and reduces the magnetism of the alloy, but at the same time reduces the stacking fault energy (SFE) of the alloy significantly and changes the type of the rolling texture which makes it difficult to obtain sharp recrystalization annealing cubic texture. Therefore, obtaining higher proportion of W element baseband with sharp cubic texture has become a research focus in this field.In this paper the Ni-8%W alloy and the composite nickel-tungsten alloy were prepared by method of powder metallurgy. The above materials were cold rolled for numerous times with a low thickness reduction per pass (the ultimate deformation is approximately94%)and the samples were annealed by one-step annealing(OSA) and two-step annealing(TSA) processes after rolling. Test methods and technologies including optical microscopy(OM), scanning electron microscopy(SEM), electron back scattering diffraction(EBSD), X-ray diffraction(XRD) were used to test and characterize the microstructure, composition, macro and micro texture of the alloy. Combining with the test results, the influence of the proportion of W element as well as different annealing processes on the formation of recrystalization cubic texture has been analyzed.For the Ni-8%W alloy, Brass-type texture formed in the process of cold rolling and the content of C and S texture reduce gradually while the B texture increases with the increase of rolling deformation due to the addition of W element which reduces the SFE of the alloy and promotes twinning. The full width at half maximum(FWHM) estimated by X-Ray (111)phi-scan of OSA and TSA were12.4°and12.1°and the volume fraction of cubic texture are10.1%and20.2%respectively, neither of them exhibited sharp cubic texture. Copper-type texture has not been obtained in the cold rolling process which makes it difficult to form sharp cubic texture after recrystallization annealing, however comparatively speaking TSA is beneficial to increase the content of cubic texture.For the composite nickel-tungsten alloy, the pole figure of high W layer is more desultory than low W layer and there are many miscellaneous orientations which are not conducive to the formation of cubic texture. FWHM of low W layer after annealed at1200℃is10.8℃and the volume fraction of cubic texture is29.2%. EBSD results show that the grains of the sample are uneven with larger grains almost all in cubic orientation. The volume fraction of cubic texture increases to85.3%after the secondary annealing treatment of heating at1250℃for2h and cooling with furnace. Strong cubic texture has been obtained in composite baseband due to the size advantage with which grains in cubic orientation can annex other grains gradually in the annealing process.Through research this paper provides not only theoretical basis for the formation of cubic texture but also experimental basis for subsequent researches.