Isothermal compression testing of Ti–5.8Al–3Sn–5Zr–0.5Mo–1.0Nb–1.0Ta–0.4Si–0.2Er titanium alloy is performed on a Gleeble-3500 thermal simulator, and the corresponding microstructures are analyzed to clarify the softening mechanism and participates evolution. A constitutive equation compensated by strain has been established to describe the hot deformation behavior of the alloy. The deformation activation energies are calculated to be 369760.93–699310.86 J/mol in α + β two-phase region and 268030.03–325800.41 J/mol in β single-phase region. At a temperature of 880 °C, the main softening mechanism is the continuous dynamic recrystallization of lamellar α colony, controlled by the mechanical rotation of the sub-grain followed by dislocation climbing and annihilation by diffusion. Meanwhile, the dominant softening mechanism is the discontinuous dynamic recrystallization of β phase during the deformation at temperatures of 920 °C–1080 °C. Silicide containing Er with an average diameter of 20 nm is formed during the water quenching.

The present study was conducted to predict the hot deformation behavior of the as-forged Nitinol 60 shape memory alloy by using the Arrhenius type, multiple-linear, and artificial neural network (ANN) models. The acquired flow stress data from isothermal hot compression tests in a temperature range of 650–850 °C under strain rate range of 0.01–1 s−1 were used to calculate the material constants for establishing the corresponding constitutive equations. Furthermore, a comparative study has been made on the capability of the aforementioned models to predict the high-temperature deformation behavior by comparing the prediction relative errors, average absolute relative error, and correlation coefficient. The results show that multiple-linear model predicts the flow behavior more accurately than the Arrhenius type model. The ANN model is much more efficient and has a better prediction power for the as-forged Nitinol 60 alloy than both the Arrhenius type and multiple-linear models.

Aiming to clarify the effects of initial states on hot deformation behavior of a powder metallurgy nickel-based superalloy FGH96, specimens in hot isostatic pressed (HIPed) and solution states were isothermally compressed in the temperature range of 1000–1150 °C and the strain rate range of 0.001–1.0 s−1. It revealed that the flow behavior of FGH96 was dependent on the initial states, in which the deformation resistance was higher in the solution state than that in the HIPed state at evaluated temperatures, and the differences became less when the temperature was higher than the γ′ dissolution temperature. The calculated hot activation energy using peak stresses are 590 and 1285 kJ mol−1 for HIPed and solution specimens. Comparison with HIPed specimen, the efficiency of power dissipation (η) in solution specimen is less, and the optimum workability regime moves to higher temperatures. Cracking and in-grain shear bands were observed in the specimens when compressed in flow instability areas.