Cold-rolled Ti-Al-V-Zr-Fe titanium alloy tubing with outstanding tensile properties

Increasing the operating pressure of the hydraulic lines is one of the directions to improve the comprehensive performance of the hydraulic system of an aircraft. However, the existing Ti-3Al-2.5V (limited strengths) and Ti-6Al-4V (poor cold formability) alloy tubing are not applicable to the hydraulic lines with an operating pressure over 28 MPa. In this work, a new type of Ti-Al-V-Zr-Fe titanium alloys were developed and the thin-walled seamless tubing was fabricated by cold rolling. After being annealed at 550 °C, Ti-4Al-2V-1.2Zr-0.3Fe (σb=1029 MPa, δ = 19%) and Ti-4.5Al-3V-1.5Zr-0.45Fe (σb=1102 MPa, δ = 18%) alloy tubing have outstanding room temperature tensile properties mainly due to dislocation strengthening. In addition, the strong radial textures in Ti-Al-V-Zr-Fe titanium alloy tubing, which increase the average Schmid factors under axial tensile loads, play a vital role in the strengthening contributions from dislocations and in the plastic deformation mechanisms. This work is of theoretical importance and practical value for developing aerospace hydraulic tubing with an excellent combination of mechanical properties.