The Study On The Texture Of Ni-W Substrates

The research and development on the second generation of high temperaturesuperconducting YBCO tapes are very exciting subjects. The Problem in obtaining longsuperconducting tapes can be solved by depositing the YBCO films on the tough substrates.Ni-W alloys are widely preferred as candidate substrates for its strong cube texture,improved strength and the low hysteresis losses.In order to obtain the high density and homogeneous Ni-W alloys, in this work, theNi-W alloys have been fabricated by spark plasma sintering furnace. The influences ofsintering parameters on the Ni-W compacts density were studied. The results showed thatthe higher temperature of sintering and slower heating rate is more beneficial for obtaininghigh density Ni-W compacts. It was also found that the vacuum of sintering plays anunimportant role on the samples density.The influences of rolling reduction and W contents on rolling textures were studied byX-rays; The relationship between recrystallisation textures of Ni-5%W and Ni-3%Wsubstrates and various factors such as the approaches of cold rolling and annealing, thecold rolling reduction as well as annealing temperatures have been studied systematically;The magnetisation M(T) and hysteresis loops of Ni-W substrates with different Wcontent were also measured; The mechanism of textmres formation and transition duringrecrystallisation were simulated by Monte Carlo method.The results obtained are as follows:1 .The brass orientation is more easily formed in the substrates with the increase of Wcontents, especially for the Ni-W alloys with W contents＞5 at.%. Therefore larger Wcontents＞5 at.% is not helpful for the formation of cube texture during annealing.2.The copper and S orientations, and thus the final cubic texture, increase with thecold rolling reduction;3.The heavier cold rolling reduction; with intermediate annealing in the rolling process;higher temperature of annealing and a two-step recrystallisation annealing are beneficial inachieving a stronger cube texture in Ni-W substrates; 4. The hysteresis losse decreases with the increase of W contents;5. Through the Monte Carlo simulation, the relationship between the volume fractionof several kinds of textures and the annealing time was given out. The simulation resultsare in accordance with the experiment results.Shape cube-textured Ni-5%W substrates have been fabricated with both 99.9% purityNi powder and 99% Ni powder.