Deformation And Recrystallization Texture Of Cu-44Ni Alloy Substrates For Coated Conductors

Non-ferromagnetic Cu-Ni alloys have been considered as hot topics in the study of high temperature coated superconductor.At present,strong cube textured Cu-Ni substrates were obtained by RABiTS process successfully,but there is very little effort to investigate the mechanism of cube texture formation in the alloy.Therefore,we have chosen no ferromagnetic(T=77K)Cu-44 Ni alloy as the research object.And the evolution of micro-hardness,microstructure and micro-texture during the rolling deformation and recrystallization annealing has been systematically studied.Furthermore,the focus of the research was to analyze the mechanism of recrystallized cube texture formation in Cu-44 Ni substrates.The research about cold-rolled microstructure of Cu-44 Ni alloys shows that: After cold rolling,the typical pure metal or Cu-type deformation texture formed,which is characterized by the development of preferred orientation along the ?-fiber running from the Cu orientation {112}<111> over the S orientation {123}<634> to the Brass orientation {011}<211>.And this texture becomes more pronounced with increasing rolling reduction.The microstructure in ND-RD section of substrates evolved from MBs to LBs,there is almost LB structure which is parallel to rolling reduction in the high deformation substrates.Furthermore,the misorientation across the orientation gradient in the cube bands increases with increasing deformation,which create the favorable conditions for nucleation of cube grain.The effects of cold rolling reduction and annealing temperatures on the formation of cube texture and microstructural evolution have been investigated in Cu-44 Ni alloy.The results showed that the recrystallized cube texture is strengthened by either increasing the rolling reduction or increasing the annealing temperature.And the strong cube texture can be observed for the severely cold-rolled(> 90%)alloy after annealing at high temperature(> 900 °C).After annealing at 1100 °C for 1 h,the 95% cold-rolled Cu-44 Ni revealed that the fraction of the cube texture reaches 98.5%,and the fractions of HAGBs and ?3 boundaries are 3.1% and 2.2%,respectively.The research about cube texture of nucleation mechanism in the low temperature annealing shows that: the traditional orientation growth theory may not be applicable the Cu-44 Ni alloy since an almost negligible presence of boundaries defined by the 30°~40°<111> relationship between the cube grains and their surroundings.At the early stage of recrystallization,the cube orientation did not have any advantage on nucleation,but the average cube grain size is comparatively large than other nucleus.And cube grains have obvious grew up rate advantage during annealing at low temperature and high temperature annealing,namely the size advantage.And this advantage becomes more and more obvious with increasing annealing time.The research about cube grain growth stage in the high temperature annealing shows that: strong cube texture formation is strongly related to the reduction of non-cube grains with small grain size in the early stage of grain growth;The enhancement of cube texture depends mainly on the consuming of the cube twins and small cube grains in the later stage of grain growth.