Residual stress evolution and tailoring of cold pilgered Ti-3Al-2.5V tube

Abstract

Cold pilgering has been considered as one of the preferred fabrication technologies for high-strength titanium alloy tube. However, the complex multi-pass thermo-mechanical loading histories in whole cold pilgering, viz., multi-stroke rolling and annealing as well as surface strengthening treatment might significantly influence the inhomogeneous deformation and residual stress which closely related to the fatigue and other service performances of tube products. The objective of this manuscript was to clarify the residual stress evolution characteristics in cold pilgering of high-strength titanium alloy tube while to propose an efficient approach for the tailoring of the residual stress. The residual stress distribution features at different deformation zones during cold pilgering were numerically investigated base on the verified finite element model. On account of the coordination of inhomogeneous deformation along the tube wall, the cold pilgered tube exhibited residual tensile and compressive stress on outer and inner surface, respectively. The effects of key process parameters on the residual stress of the cold pilgered tube were explored as well as the relevant inhomogeneous deformation features were discussed, the results showed that the value of residual stress could be affected by the variation of the Q value and area reduction but independent with other parameters. By combining the experiment, it can be also concluded that the residual stress states of the cold pilgered tube were maintained with the variation of the process parameters of cold pilgering and annealing. Furthermore, aiming at the residual stress tailoring and service performances improvement of the tube, the magnetic abrasive finishing (MAF) was introduced while the measurement results indicated that large residual compressive stress could be generated on the outer and inner surface of the tube simultaneously.