High-Temperature Formability and Friction Regulation Mechanism of TA17 Titanium Alloy with Typical Microstructures

This study aims to clarify the effects of initial microstructure and friction coefficient on the high-temperature formability of TA17 titanium alloy. Three typical microstructures were prepared via different annealing processes to provide theoretical and experimental support for hot forming process optimization. Existing studies on TA17 titanium alloy mainly focus on its room-temperature mechanical properties and corrosion resistance, while quantitative investigations on the influence of different initial microstructures on its high-temperature forming limit are still scarce. Moreover, the temperature evolution characteristics of the friction coefficient for TA17 alloy and its quantitative influence on deep-drawing forming limit remain unclear, and few studies have considered the effect of initial microstructure and friction coefficient on the high-temperature formability of titanium alloys. Combined with high-temperature tensile tests, high-temperature friction- wear tests and finite element (FE) simulation, the effects of microstructure characteristics and friction coefficient on the high-temperature formability of TA17 alloy were systematically investigated. The results show that the equiaxed microstructure obtained by annealing at 850 °C for 2 h exhibits the best high-temperature plasticity at 900 °C and strain rate of 0.01 s^-1, while the plasticity of Widmanstätten and bimodal structures is significantly reduced. The high-temperature friction coefficient of TA17 alloy decreases sharply with increasing temperature, dropping from 0.56 at 650 °C to 0.19 at 800 °C, and can be stably controlled below 0.2 in the optimal forming temperature range of 800-900 °C. The friction coefficient has a remarkable influence on the deep-drawing forming limit: as the friction coefficient increases from 0.05 to 0.2, the limit principal strain and limit punch stroke decrease accordingly. This study reveals that fine equiaxed microstructure and low friction coefficient can enhance the high-temperature forming formability of TA17 titanium alloy. In actual industrial hot forming processes, it is recommended to use TA17 alloy with equiaxed microstructure and control the friction coefficient below 0.15 by using high-temperature lubricants, which can effectively improve the forming quality of complex aerospace structural components.