New Constitutive Model for Hot Deformation Behaviors of Ni-Based Superalloy Considering the Effects of Initial δ Phase

The hot deformation behaviors of a typical Ni-based superalloy are investigated by uniaxial tensile tests over wide ranges of strain rate and deformation temperature. The experimental results show that the flow stress is sensitive to strain, strain rate, and deformation temperature. Especially, initial delta phase (Ni3Nb) has a special effect on the flow stress. The initial delta phase can enhance the work-hardening behavior and result in the increased peak stress at relatively small strains. With the further straining, the initial delta phase can stimulate the dynamic recrystallization and promote the dynamic-softening behaviors. Considering the synthetical effects of deformation temperature, strain, strain rate, and initial delta phase on the hot deformation behaviors, a new phenomenological constitutive model is proposed. In the proposed model, the peak stress and material constant are expressed as functions of Zener-Hollomon parameter and the initial content of delta phase. A good agreement between the predicted and measured results shows that the proposed model can give an accurate and precise estimate of the hot deformation behaviors for the studied Ni-based superalloy.