The improved physically-mechanism constitutive model for a Ni-Mo-Cr-based superalloy with the pre-precipitation of μ phase in hot forming

Abstract

High-temperature deformation features of the Ni-Mo-Cr-based superalloy with the pre-precipitation μ phase are researched utilizing thermal compression experiments. For unravelling the nucleating characteristics of substructures and interacted with μ phase in hot deformation, the transmission electron microscope (TEM) is utilized. Electron backscatter diffraction (EBSD) is employed to explore the nucleating/growth mechanisms of dynamic recrystallization (DRX). An improved physically-mechanism (IPM) model is set up for reconstituting flow stresses and microstructural evolution. The investigated results demonstrate that high-density subgrains/dislocation loops can be mainly formed by dislocations entanglement and the pinned mechanism of μ phase/grain boundaries. In addition to discontinuous/continuous DRX nucleating mechanisms, the nucleating mode induced by twins and the stimulated nucleus by μ phase are also detected. The coarsen of DRX grains is substantially repressed with reducing compressed temperature or ascending strain rate, which exacerbates the inhomogeneous scatter of grains. Meanwhile, the contents of low angle grain boundaries (LAGBs) sensibly increase, owing to the sharply increase of substructures. The superior consistence of reproducing and tested results suggests the IPM model can be employed to exactly forecast the stresses, grain size as well as DRX fraction of the investigated Ni-Mo-Cr-based superalloy with the pre-precipitation μ phase.