Investigating the Effect of Strain on Deformation Behavior and Microstructural Evolutions During Non-Isothermal Hot Compression of Ti‑۶Al‑۴V Alloy

Ti-۶Al-۴V alloy is a two-phase alloy that has excellent mechanical properties and good corrosion resistance. This alloy is widely used in the manufacture of aircraft engine components such as fan blade frames and fan discs. In the present study, the non‑isothermal deformation behavior of Ti-۶Al-۴V alloy and the effect of strain on its microstructural evolution were investigated. For this purpose, samples were compressed at a constant strain rate of ۰.۰۱ s⁻¹ under non‑isothermal conditions with a cooling rate of about ۰.۶ °C/s, starting from ۹۵۰ °C. The effect of increasing strain on the volume fraction of secondary alpha lamellae, their aspect ratio, and their thickness was examined by interrupting the test at strain levels of ۰.۲, ۰.۴, and ۰.۸. The results showed that during non‑isothermal deformation, the volume fraction of the secondary alpha lamellae increases significantly with increasing applied strain. Regardless of the temperature drop, deformation promotes the formation of numerous fine needle‑shaped secondary alpha lamellae. The microstructural observations showed that the volume fraction of alpha lamellae increased by about ۱۰.۵%, in the sample deformed to a strain of ۰.۸. As the strain increases, the aspect ratio of the secondary alpha lamellae decreases. At a strain of ۰.۸, ۵۴% of the alpha lamellae exhibit an aspect ratio of less than ۲.۵. At low applied strains (up to ۰.۴), the dominant effect of strain is the increase in the volume fraction of secondary alpha, and the prevailing mechanism of alpha‑lamella spheroidization is the fragmentation of the lamellae through buckling. However, at higher strains (۰.۴-۰.۸), the dominant deformation mechanism shifts, and spheroidization of the alpha lamellae mainly occurs through the formation of thermal grooves and boundary splitting. In addition, at low strains (۰.۲-۰.۴), both the formation rate of secondary alpha lamellae and their spheroidization rate are higher than those observed at larger strains (۰.۴-۰.۸).

کلیدواژه ها:

Hot deformation ، Non-isothermal compression ، Spheroidization ، Ti-۶Al-۴V alloy ، Secondary alpha