Constitutive Modeling and Microstructural Evolution of Hot Deformed Ti-۶Al-۴V Alloy Starting with Initial Fully Lamellar Microstructure

Ti–۶Al–۴V alloy has gained widespread popularity due to its extensive applications, including nuclear and aircraft structural components, machine parts, and notably medical equipment parts. Gaining a comprehensive understanding of the material's deformation behavior and microstructure evolution during the hot working process is crucial in order to attain the desired dimensions and the final mechanical properties of a product. In this study, the hot deformation behavior of the fully lamellar Ti-۶Al-۴V alloy was investigated using the hot compressive test at different temperatures of ۷۰۰-۱۰۵۰ ◦C and strain rates of ۰.۰۰۱-۱ s-۱. The deformation stress, strain rate, and temperature were correlated using Arrhenius constitutive equations in α + β and β-phases. Finally, the activation energy values were calculated at almost ۶۳۰ kJ/mol and ۲۹۳ kJ/mol in α + β and β-phases, respectively. Based on true stress-strain curves, dynamic recrystallization was the dominant hot deformation mechanism at strain rates of ۰.۱ s-۱ or lower. On the other hand, dynamic recovery occurred at a low temperature of ۷۰۰ ◦C, and high temperatures of ۱۰۰۰-۱۰۵۰ ◦C with high strain rates of ۱ s-۱. The dynamic strain aging was visible as the serrated effects on deformation curves. The hot deformed microstructures of Ti-۶Al-۴V alloy were changed through geometric dynamic recrystallization, lamellar kinking and fragmentation, and globularization. Microstructural evolution at low temperatures immediately initiated after peak stress with dynamic recrystallization and lamellar kinking. At high temperatures of ۸۵۰-۹۰۰ ◦C, globularization was combined with other softening mechanisms, and the lamellar microstructure was changed to equiaxed grains.

کلیدواژه ها:

Ti-۶Al-۴V alloy ، Hot deformation ، Lamellar microstructure ، Dynamic recrystallization ، Constitutive modeling