Effect of annealing process on microstructure and electrical conductivity of cold-rolled Ti microalloyed conductive steel

To improve the mechanical and electrical conductivity of Ti micro alloyed steel, the effect of annealing temperature and annealing time on the mechanical and conductivity properties were investigated. The microstructure evolution of the test steels after annealing and the precipitation behavior of Ti(C,N) particles in the ferrite phase was studied by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that the steel has the most excellent comprehensive properties after annealing at 630 °C for 2 h, its tensile strength, yield strength, elongation and conductivity reach to 522 MPa, 414 MPa, 30% and 13.86%IACS, respectively. The mechanism is that during the annealing process, Ti atoms promote the precipitation of C and N solution elements from the matrix, and the precipitated second phase prevents the migration of some dislocations, ensures its mechanical properties, and improves electrical conductivity at the same time. The excellent mechanical properties of the tested steels after deformation heat treatment are attributed to precipitation strengthening, substructure strengthening and work hardening, and good conductive properties are from the reduced dislocation density in grains and the precipitation of solid solution atoms. •The microstructure, dislocations and precipitated phases of the test steel were observed and analyzed.•The calculated yield strength (σy) of the steel after annealing is in good agreement with the measured value.•The strength of steel comes from work hardening, precipitation strengthening and annealing softening, and the electrical conductivity comes from dislocations and precipitation.•The precipitation of steel scatters electrons, but the scattering effect of lattice distortion is far from that of solute atoms.