Process Optimization and Fatigue Properties of Vacuum Brazed Titanium Alloy

Titanium alloy weldment has many advantages such as light weight, high strength and corrosion resistance, etc. It has been widely used in aerospace, machinery and chemical industries. Vacuum brazing is a high-quality welding process that the materials are uniformly heated in a vacuum environment. The welding process is of great importance for the production of titanium alloy parts that are difficult to weld. The mechanical properties and durability analysis of vacuum brazed weldments are worth studying. This project will be divided into two parts to explore vacuum brazed Ti-6Al-4V weldment. First of all, the optimal process parameters are set up. Ultimate tensile strength and fracture toughness are selected as targets. Single-objective and multi-objective optimization analyses are applied to meet with different design requirements. The second part is to obtain the fatigue crack growth rate and crack closure stress data, and to investigate the effects of stress ratio and overloading on crack growth. The optimal fatigue crack growth analysis model of this weldment is established under variable amplitude loading history. In addition, we will compare the difference between fatigue life assessment models of vacuum brazed components (belonging to diffusion welding) and electron beam welded components (belonging to fusion welding). The project is expected to solve the following problems: (1) the selection of optimal process parameter combination for vacuum brazed titanium alloy under different design concepts, (2) the fatigue design of vacuum brazed titanium alloy, (3) complete fatigue analysis methods for titanium alloy weldments both with and without cracks. The results of this project will have academic value and promote the industrial application of titanium alloy.