Fatigue Behavior of Additively Manufactured IN718 with Columnar Grains. Issue 3 (23rd November 2020)

• Record Type: Journal Article
• Authors: Ye, Wenye; Akram, Javed; Mushongera, Leslie T.
• Is Part Of: Advanced engineering materials. Volume 23:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-11-23
• Subjects: columnar IN718 polycrystals -- crystal plasticities -- fatigue crack initiations -- stored energies; Materials -- Periodicals; 620.11
• DOI: 10.1002/adem.202001031
• Languages: English
• ISSNs: 1438-1656

Abstract

Abstract : Fatigue failure of polycrystalline materials is often dominated by crack initiation processes, which are strongly influenced by salient features existing in the microstructure. Herein, a crystal plasticity framework based on the finite element method is used to quantitatively assess the mechanistic drivers existing in columnar IN718 polycrystals for fatigue crack nucleation. To that end, microstructurally differing polycrystalline samples are subjected to strain‐controlled cyclic loading at ambient conditions to elucidate the microstructural mechanisms of fatigue damage. 2D grain structures obtained from the cellular automata (CA) simulations of the additive manufacturing of IN718 are utilized to construct representative 3D microstructures for use in computational analyses. A criterion related to the stored energy density (SED) is used to predict the scatter in fatigue crack nucleation life. This criterion presents a unique and consistent approach toward predicting fatigue crack initiation at the microstructural scale. It is demonstrated that SED is necessary and sufficient to drive crack nucleation in low cycle fatigue. The results show that grain boundaries are the preferred crack initiation sites. Abstract : A quantitative assessment using the crystal plasticity finite element method is conducted on the 3D representative microstructures of columnar IN718 polycrystals for fatigue crack nucleation. The approach predicts fatigue life with a criterion of stored energy density (SED) at the microstructural scale. Preferred sites by fatigue cracks are presented in the representative microstructure.