Hot deformation behavior of a novel alpha plus beta titanium alloy TIMETAL®407

The hot deformation behavior of a newly developed alpha + beta titanium alloy TIMETAL (R) 407 (Ti407) was characterized in starting transformed-beta microstructure at different temperatures (T = 650-950 degrees C) and strain rates (epsilon = 10(-3) -1 s(-1)) using hot-compression testing. The Arrhenius type constitutive equations are de-veloped for Ti407 and the activation energy for deformation is determined as 333.1 and 179.8 kJ/mol in the alpha and beta dominated phases, respectively. The processing and strain-rate sensitivity maps of Ti407 were gen-erated at true strain, epsilon= 0.5 on the basis of modified dynamic materials model (DMM) proposed by Murty and Rao. Results obtained from the maps and microstructural analysis of the deformed specimens indicates three distinct stable domains (I-A, II-A and I-B) within the examined conditions. Out of the three stable domains, Domain I-A occurring in the alpha + beta phase field (T = 800-860 degrees C and epsilon = 6.3 x10(-2) -1 s(-1)) and Domain I-B in the beta phase field (T = 900-950 degrees C and epsilon = 10(-3) -1 s(-1)) were optimum domains for possible hot working of Ti407. The peak in the efficiency of power dissipation of about 58% occurred in Domain I-A at 850 degrees C/1 s(-1), where dynamic spherodization of alpha lamellae occurred. In Domain I-B, formation of fine dynamically recrystallized beta grains was observed with peak in power dissipation efficiency of about 60% at 950 degrees C/10(-3) s(-1). Ti407 showed evidence of flow instabilities like flow localization and kinking of alpha lamellae in the predicted unstable zones identified from the processing map. The hot workability of Ti407 on the basis of expanding or shrinking stable regimes for processing is also compared with CP-Ti and Ti-6Al-4V alloys at identical strain rates and temperatures relative to the beta-transus. Finite element method (FEM) software DEFORM (R) - 3D was used for forging simulation at the peak in deformation efficiency condition in various stable domains to evaluate the flow response and distributions of stress/strain in the forged billets. (C) 2022 Elsevier B.V. All rights reserved.