Effect of Texture on Circumferential Tensile Properties of TA18 Titanium Alloy Tubing

Taking advantage of texture strengthening, the TA18(Ti-3Al-2.5V) titanium alloy tubing with tensile strength of 860 MPa as well as a good combination of mechanical properties and high formability was developed. While the contractile strain ratio (CSR) of such tubing must be greater than 1.3 to meet the current standard, the upper limit value is not specified. In this paper, a fixture was designed for the hoop tension of tubing with a small diameter, and the mechanical properties in the hoop direction of tubing with different CSR values was tested. The effects of texture on the circumferential strength was analyzed. Results show that the optimal CSR value for the yield strength is 1.75, while a higher or lower value would lead to a decrease of the strength. Additionally, based on the pole figures and the orientation distribution function (ODF), the essence of the above regulation is well explained from microscopic aspects. Lower circumferential strength of hydraulic tubing will result in poorer fatigue life of hydraulic system in service; hence the upper limit value, not just the lower limit value, of CSR should be controlled. This investigation will be of theoretical significance and application value for the development of safe and reliable aerospace hydraulic systems. © 2020, Science Press. All right reserved.