Optimizing Structural and Mechanical Properties of an Industrial Ti-6246 Alloy below β-Transus Transition Temperature through Thermomechanical Processing

This study aims to investigate the effect of hot deformation on commercially available Ti-6246 alloy below its beta-transus transition temperature at 900 degrees C, knowing that the alpha -> beta transition temperature of Ti-6246 alloy is about 935 degrees C. The study systematically applies a thermomechanical processing cycle, including hot rolling at 900 degrees C and solution and ageing treatments at various temperatures, to investigate microstructural and mechanical alterations. The solution treatments are performed at temperatures of 800 degrees C, 900 degrees C and 1000 degrees C, i.e., below and above the beta-transus transition temperature, for 9 min, followed by oil quenching. The ageing treatment is performed at 600 degrees C for 6 h, followed by air quenching. Employing various techniques, such as X-ray diffraction, scanning electron microscopy, optical microscopy, tensile strength and microhardness testing, the research identifies crucial changes in the alloy's constituent phases and morphology during thermomechanical processing. In solution treatment conditions, it was found that at temperatures of 800 degrees C and 900 degrees C, the alpha '-Ti martensite phase was generated in the primary alpha-Ti phase according to Burger's relation, but the recrystallization process was preferred at a temperature of 900 degrees C, while at a temperature of 1000 degrees C, the alpha ''-Ti martensite phase was generated in the primary beta-Ti phase according to Burger's relation. The ageing treatment conditions cause the alpha '-Ti/alpha ''-Ti martensite phases to revert to their alpha-Ti/beta-Ti primary phases. The mechanical properties, in terms of strength and ductility, underwent an important beneficial evolution when applying solution treatment, followed by ageing treatment, which provided an optimal mixture of strength and ductility. This paper provides engineers with the opportunity to understand the mechanical performance of Ti-6246 alloy under applied stresses and to improve its applications by designing highly efficient components, particularly military engine components, ultimately contributing to advances in technology and materials science.