Improving surface quality of oxygen-free copper tube via grain growth inhibition with La microalloying

The effect of La microalloying on microstructure evolution of oxygen-free copper tube annealed at elevated temperature was investigated. Different with the significant grain growth in La-free copper tube, growth behavior of La microalloyed tube is effectively inhibited. Meanwhile, Cu6La particles are detected with mainly segregating near annealing twin boundaries but less at grain boundaries. With such experimental observations, a new mechanism for constrained growth of recrystallized grain is proposed with pinning of Cu6La particle coupled with annealing twin dragging. Moreover, refined microstructure is maintained for La microalloyed tube after elevated temperature, which greatly improves the surface quality during secondary bending and flattening processes.