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The deformation mechanisms and dynamic softening behavior of a Ti–6Al–4V alloy with thick lamellar microstructures are studied by uniaxial hot tensile tests. The true stress first rapidly reaches a peak value because of the rapid dislocations proliferation and tangle, and then gradually decreases due to the dynamic softening with raising the deformation amount. The dynamic softening behavior is mainly induced by the severe dynamic globularization of lamellar α phases. The globularization of α phase is always accompanied by the formation of high‐angle grain boundaries (HAGBs). The fraction of globularized α phases increases with the increasing deformation temperature. The fracture mechanism is microvoid coalescence, i.e., in the initial stage of tensile deformation, the microvoids begin to emerge. With the increasing deformation amount, the number of microvoids increases, and the microvoids accumulate and accelerate to propagate until the final fracture. According to the experimental flow stress curves, a modified Arrhenius‐type equation and a Hensel–Spittel (HS) model are developed to forecast the flow stresses. The average absolute relative error of the established strain‐compensated Arrhenius‐type (SCAT) and HS models are 6.108% and 3.385%, respectively. Both models can be well used to describe the hot tensile flow characteristics of the Ti–6Al–4V alloy with thick lamellar microstructures.

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The flow behavior of a high‐strength Ti alloy (Ti‐55511) in the β region is studied by hot compressive experiments. A dislocation density–based constitutive equation, together with processing maps, is established to describe the flow behavior and hot workability of the studied Ti alloy. It is found that the strain rate (εfalse˙) and temperature (T) distinctly influence the hot compressive deformation behavior. The flow stress increases distinctly with a rising εfalse˙ or reducing T. The main softening mechanism in the β region is dynamic recovery (DRV). The established constitutive equation based on the work hardening (WH) and DRV mechanisms has the desired prediction accuracy, and the correlation coefficient between the predicted and experimental results is 0.9912. The processing maps indicate that a high strain rate (0.4–10 s−1) easily causes unstable deformation, whereas low and medium strain rates (0.001–0.2 s−1) are suitable for hot compressive deformation of the studied alloy.

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Uniaxial creep tensile experiments are performed to study the influences of initial δ phase (Ni 3 Nb) on the creep features and fracture behaviors of a nickel-based superalloy. Experimental results show that the creep features and fracture behaviors of the researched superalloy are closely relevant to the volume fraction of initial δ phase. The minimum creep rate increases with the increased volume fraction of initial δ phase. The appropriate volume fraction of initial δ phase can improve the creep resistance and plasticity. So, the rupture time and the elongation to fracture initially increase, when the volume fraction of initial δ phase is relatively low, and then decrease with the increase of volume fraction of initial δ phase. Additionally, with the increased initial δ phase, the failure mode changes from a typical intergranular fracture to the mixed fracture pattern of ductile intergranular and cleavage fracture.

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