Influence of short-time annealing on the evolution of the microstructure, mechanical properties and residual stress of the C19400 alloy strips

Abstract

The changes in the tensile strength, microhardness, electrical conductivity and residual stress of the C19400 alloy strips annealed at 100–500 ℃ for a short time were studied. The coordinated control mechanism of the high strength and low residual stress of the C19400 alloy strips by short-time annealing was revealed. The results show that annealing at 200 °C can maintain high strength and reduce the residual stress. When annealed at 200 °C, the tensile strength is only 0.6 % lower than that of the original state, while the residual stresses of transverse direction and rolling direction are 47.2 % and 90.9 % lower than that of the original state, respectively. Reducing the volume fraction of Brass, Copper and S textures is beneficial for controlling the residual stress of the C19400 alloy. Most remarkably, compared with the original state, after annealing at 300 ℃, the tensile strength and microhardness increase from 428 MPa to 432.5 MPa and 141.6 HV to 144.8 HV, respectively. When annealing at 400–500 ℃, the tensile strength and microhardness decrease significantly. The main influencing factor of annealing hardening and softening is dislocation density. In the former, dislocation blocking increases the dislocation density during low-temperature annealing, while in the latter, recovery and recrystallization occur, and the dislocation density decreases after high-temperature annealing. The results provide a reference for improving the performance of ultrathin C19400 alloy strips.