A comparative study on the hot deformation behavior of Ti5Al5Mo5V3Cr and newly developed Ti4Al7Mo3V3Cr alloys. (March 2019)

• Record Type: Journal Article
• Authors: Momeni, A.; Abbasi, S.M.; Sadeghpour, S.
• Is Part Of: Vacuum. Volume 161(2019)
• Page Start: 410
• Page End: 418
• Publication Date: 2019-03
• Subjects: Beta Ti alloys -- D-electron method -- hot compression -- Dynamic recovery -- Dynamic recrystallization -- Constitutive analysis; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2019.01.008
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Hot deformation behavior of Ti-5553 and newly-developed Ti-4733 β-Ti alloys were compared by hot compression tests at 930–1080 °C and strain rates of 0.001–1 s −1 . The flow curves and microstructures showed that dynamic recovery and partial continuous dynamic recrystallization are the dominant microstructural mechanisms at hot working condition. It was observed that the flow stress of Ti-4733 lies over that of Ti-5553. Using the M ¯ d ¯ - B ¯ O ¯ diagram, Mo equivalent number and the valence electron count, it was shown that β-phase in Ti-4733 is more stable than that in Ti-5553. The higher strength of Ti-4733 was attributed to the more stability of β and its higher Mo equivalent number. While the β quenched microstructure in Ti-5553 contained parallel layers of α′ martensite, it was absence in Ti-4733 due to the more stability of β. Using the hyperbolic-sine constitutive equation the values of apparent activation energy for Ti-5553 and Ti-4733 were determined as 380 and 315 kJ/mol, respectively. The Kocks-Mecking dislocation evolution model was used to model the flow curves. The recovery and hardening parameters for Ti-4733 in the developed model were found lower than those for Ti-5553. The model could satisfactorily predict the experimental flow curves at various conditions. Highlights: Beta-phase in Ti-4733 and Ti-5553 is semi-stable and unstable, respectively. Stability and strength of beta-phase increases with increase in valence electron count. Ti-4733 exhibits higher strength than Ti-5553 at elevated temperatures. Activation energy for hot deformation decreases with molybdenum equivalent. Flow curves of Ti-4733 are successfully modeled by Kocks-Mecking equation.