Study Of Globularization In Ti-6al-4v Alloy During Non-Isothermal Multiple Forging And Annealing
In present work the mechanisms of globularization i.e. breaking of initial α colony structure during multiple forging and post deformation annealing process at different temperatures (700°C to 950°C) has been analyzed. A workpiece (Ø94 mm x 120 mm) of Ti-6Al-4V alloy with starting initial α-colony structure was heated at 850°C and subjected to successive upsetting and drawing operations without intermediate heating, followed by water quenching. The deformed Ti-6Al-4V alloy consists of heterogeneous microstructure with kinked, sheared and unreformed α lamellae. Microstructure evolution mechanism during successive upsetting or drawing operations is proposed here. Globularization of thin inter-lamellar β phase was observed after post deformation annealing at 800°C. The process of static globularization was found to be accelerated by increase in annealing temperature above 900°C via mechanisms like boundary splitting, edge spheroidization and cylinderization.
Index Terms- Annealing, Globularization, Non-isothermal multiple forging, Ti-6Al-4V alloy