Hot deformation characteristics and dislocation substructure evolution of a nickel-base alloy considering effects of delta phase

The hot deformation characteristics of a nickel-base alloy with different contents of delta phase (Ni3Nb) were studied by isothermal compressive experiments. The experimental data and microstructural observation reveal that the hot compressive behavior and dislocation substructure evolution not only relate to the thermomechanical parameters (deformation temperature, strain, strain rate), but also are affected by the content of delta phase. In the initial deformation stage, the dislocation movement is significantly impeded, and the strain hardening behavior is aggravated with increasing the content of delta phase. With the further straining, delta phase exerts the ability for promoting dynamic recrystallization (DRX). Additionally, a new phenomenological constitutive model (PCM) and a deep belief network model (DBNM) are developed to reflect the influence of delta phase. The relative coefficients of the developed PCM and DBNM are 0.992 and 0.998, respectively. The error bands of flow stresses predicted by PCM and DBNM are controlled in +/- 30 MPa and +/- 20 MPa, respectively. The high predictability indicates that the developed PCM and DBNM can quantitatively reflect the hot deformation behaviors of the studied alloy with different delta phase contents. (C) 2018 Elsevier B.V. All rights reserved.