Effect of annealing time on grain boundary characteristics of C71500 cupronickel alloy tubes with different deformation

Abstract

The effect of different annealing times on microstructure and properties of C71500 cupronickel alloy tubes were studied at the temperature of 800 °C. Electron backscatter diffraction (EBSD) technique was applied to analyze the change trend of the “special” grain boundaries proportion of alloy under different processing conditions. The difference of microstructure transformation between small and large annealing deformation was analyzed. The optimal process was verified by means of grain cluster analysis, “Σ3 regeneration model” verification, the relationship between grain cluster size and grain size, and the residual stress analysis. The results show that the static recrystallization (SRX) is the main process of the 70.55% deformation alloy tube after annealing at 800 °C. With the increase of annealing time, the proportion of low coincidence site lattice (CSL) grain boundary has no obvious pattern change, but the grain size can be controlled. The static recovery is the main process for the small deformation (9.57%) alloy tube at 800 °C annealing, and the proportion of low ΣCSL grain boundary reaches 78.00% after annealing for 15 min. The ideal microstructure could be obtained by the two stages rolling processes: “70% deformation + 800°C annealing, holding for 20 min; and 9.57% deformation + 800°C annealing, holding for 15 min”.