Effects of annealing temperature on the comprehensive properties of ultrathin niobium strips

Ultrathin niobium strips with thicknesses of 20, 30, and 40 µm were prepared by an accumulative roll process. The evolution of the microstructure, texture and mechanical properties of ultrathin Nb strips with different thicknesses at different annealing temperatures was studied by an electronic universal tensile testing machine and EBSD analysis. The results show that the whole process of grain recovery, recrystallization, complete recrystallization, and grain growth occurs with increasing annealing temperature. The complete recrystallization temperature increased as the thickness increased, and ultrathin niobium strips with thicknesses of 20 µm and 30 µm were recrystallized at 1050 °C, while the 40 µm thick sample was recrystallized at 1150 °C. Furthermore, to further characterize the size effect under extremely thin thicknesses, the 20 µm ultrathin niobium strip was analyzed in detail. It was found that the texture in the cold rolling state is mainly dominated by texture 〈111〉 ND. With increasing annealing temperature, the orientation density of the γ texture 〈111〉 ND orientation density gradually decreased, but the {111} 〈110〉 texture remained the main texture. It is noteworthy that the tensile strength of the ultrathin niobium strip decreases as the annealing temperature increases, but the elongation rate is still generally low, and the tensile strength of the ultrathin niobium strip indicates that the size effect is effectively ‘the smaller, the stronger’.