Crystal Plasticity Simulation of the Microstructural Effect in Powder Metallurgy Superalloys under Dwell Fatigue Loading

Zebang Zheng,Zichao Peng

doi:10.3390/cryst12020269

Abstract

The microstructural effect, including γ’ precipitate morphology and twin grains, of dwell fatigue behavior in a powder metallurgy nickel-based superalloy, was studied using crystal plasticity modeling. Strain rate and dwell sensitivities of 923 K were quantitatively investigated. The strain accumulations, under normal and dwell fatigue loading, showed γ’ precipitate size-dependence. Strong load shedding can be observed between parent and twin grains, which was attributed to local plastic heterogeneity. Local stress and strain evolution are both faster than the macroscopic values, which threatens the safety of engine components.

Highlights

Powder metallurgy (PM) nickel-based superalloys have been widely used in aeroengine disks, owing to their excellent creep and fatigue resistance at high temperatures [1,2,3]
The stress-bearing components in the engines are generally subjected to low cycle dwell fatigue (LCDF) loading conditions
The explanation for early crack formation under dwell fatigue is that stress redistribution, namely load shedding amongst crystallographic soft–hard grain combinations occurring during the dwell period, [11] arises from the remarkable anisotropy observed in the hexagonal close-packed structure

Summary

Introduction

Powder metallurgy (PM) nickel-based superalloys have been widely used in aeroengine disks, owing to their excellent creep and fatigue resistance at high temperatures [1,2,3]. Stinville and co-authors [16,17] characterized the local strain and strain heterogeneities under fatigue loadings by employing the high-resolution digital image correlation (DIC) technique They observed that the strain concentration at grain boundaries, induced due to the resistance to slip transmission, can be up to eight times higher than the nominal strain. The aforementioned evidence indicates that plasticity localizations near twin boundaries are crucial prerequisites for fatigue responses in nickel-based superalloys and, these microstructural features need to be explicitly represented in order to capture this phenomenon. This study focuses on the fatigue responses of PM nickel-based superalloys with different precipitate sizes by employing a microstructure-based crystal plasticity modeling approach in which the grain morphology is explicitly represented, aiming to shed light on the mechanistic basis of the dwell fatigue failure

Materials and Crystal Plasticity Finite Element Framework

Findings

Conclusions