热处理及预拉伸对 TC4-0.55Fe 合金组织和力学性能的影响

This paper investigated the effects of different heat treatment processes (solution aging and double annealing) and pre-stretching on the microstructure and mechanical properties of Ti-6Al-4V-0.55Fe (TC4-0.55Fe) alloy with duplex microstructure, and the relationship between its microstructure and mechanical properties were discussed. The TC4-0.55Fe alloy microstructures and mechanical properties after solution aging and double annealing were compared, it is found that the thickness of the lamellar α phase gradually increases with the increase in aging and low temperature annealing temperature, which leads the strength of the alloy decreases and the plasticity increases. Under the solution aging treatment, the yield strength of the alloy decreases from 873 MPa at 530 °C to 862 MPa at 590 °C and the elongation increases by 3.2%. The yield strength of the double annealing heat treated sample decreases gradually with the increase in the low temperature annealing temperature, but the elongation has been greatly improved compared with the solution aged, and the best is 23.6%. Because the strength of TC4-0.55Fe alloy is not significantly improved by solution aging and double annealing, the plasticity of the double annealing sample is better than that of the solution aging when the aging and low temperature annealing temperature is 590 °C, so the double annealing process at 590 °C is selected to combine the pre-stretching strengthening, the pre-stretching is introduced between the solution and low temperature annealing. After the introduction of pre-stretching, the α phase deformation is obvious, and the precipitation-free zone (PFZ) forms. A large amount of fine secondary α phases (α_s) are precipitated in the PFZ after annealing. The annealing after the pre-stretching can improve the yield strength of TC4-0.55Fe alloy and only reduce plasticity little. Among them, the sample with 1% pre-stretching deformation has the highest content of α_s phase, the field strength is increased by 68 MPa compared with that of the double annealing, and the elongation is only decreased by 4%, the comprehensive mechanical properties are the best. According to this study, it can be concluded that the comprehensive mechanical properties of TC4-0.55Fe titanium alloy can be improved by pre-stretching and aging strengthening after solution.