Dong-Xu Wen

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 δ phase (Ni3Nb) has a special effect on the flow stress. The initial δ phase can enhance the work-hardening behavior and result in the increased peak stress at relatively small strains. With the further straining, the initial δ phase can stimulate the dynamic recrystallization and promote the dynamic-softening behaviors. Considering the synthetical effects of deformation temperature, strain, strain rate, and initial δ 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 δ 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.

Effects of initial δ phase (Ni3Nb) on hot tensile deformation behaviors and material constants of Ni-based superalloy

Abstract Effects of initial δ phase (Ni3Nb) on the hot tensile deformation behaviors and material constants of a Ni-based superalloy were investigated over wide ranges of strain rate and deformation temperature. It is found that the true stress–true strain curves exhibit peak stress at a small strain, and the peak stress increases with the increase of initial δ phase. After the peak stress, initial δ phase promotes the dynamic softening behaviors, resulting in the decreased flow stress. An improved Arrhenius constitutive model is proposed to consider the synthetical effects of initial δ phase, deformation temperature, strain rate, and strain on hot deformation behaviors. In the improved model, material constants are expressed as the functions of the content of initial δ phase and strain. A good agreement between the predicted and measured results indicates that the improved Arrhenius constitutive model can well describe hot deformation behaviors of the studied Ni-based superalloy.

Three-Dimensional Crystal Plasticity Finite Element Simulation of Hot Compressive Deformation Behaviors of 7075 Al Alloy

Three-dimensional crystal plasticity finite element (CPFE) method is used to investigate the hot compressive deformation behaviors of 7075 aluminum alloy. Based on the grain morphology and crystallographic texture of 7075 aluminum alloy, the microstructure-based representative volume element (RVE) model was established by the pole figure inversion approach. In order to study the macroscopic stress-strain response and microstructural evolution, the CPFE simulations are performed on the established microstructure-based RVE model. It is found that the simulated stress-strain curves and deformation texture well agree with the measured results of 7075 aluminum alloy. With the increasing deformation degree, the remained initial weak Goss texture component tends to be strong and stable, which may result in the steady flow stress. The grain orientation and grain misorientation have significant effects on the deformation heterogeneity during hot compressive deformation. In the rolling-normal plane, the continuity of strain and misorientation can maintain across the low-angle grain boundaries, while the discontinuity of strain and misorientation is observed at the high-angle grain boundaries. The simulated results demonstrate that the developed CPFE model can well describe the hot compressive deformation behaviors of 7075 aluminum alloy under elevated temperatures.