Microstructure Evolution and Mechanical Properties of a Novel Near-α Titanium Alloy During Hot Forging inα + β Phase Region

Abstract

The microstructure evolution and mechanical behavior of the Ti65 alloy with lamellar microstructure, a near-α high-temperature titanium alloy, were systematically investigated during hot forging in the α + β phase region. Isothermal compression experiments were conducted under different deformation parameters. The evolution of the microstructure and texture during thermomechanical processing was thoroughly characterized by SEM and electron backscatter diffraction (EBSD). In addition, the differences in mechanical properties between the initial lamellar structure and dynamically spheroidized microstructures were examined at both room and high temperatures. It was observed that dynamic spheroidization of lamellar α was promoted, and lamellae were progressively transformed into globular α with fine interlamellar β phase under appropriate thermomechanical conditions. The volume fraction of spheroidized microstructure was found to be dependent on both strain rate and temperature, with lower strain rates and higher temperatures facilitating greater spheroidization. After significant dynamic spheroidization of the lamellar structure, the maximum intensities of the texture were also markedly reduced. Mechanical testing revealed that significant improvements in tensile properties were achieved after hot forging, with both strength and ductility being enhanced. After a 70% deformation amount, the ultimate tensile strength (UTS) at room temperature was increased from 1012 to 1129 MPa, and a notable increase in high-temperature elongation was demonstrated. These performance enhancements were attributed to the refined microstructure and spheroidized α morphologies. The results indicate that controlled thermomechanical processing can be used to optimize strength–ductility balance in high-temperature titanium alloys developed for aerospace applications.