Title: Understanding the low cycle fatigue of additive manufactured Inconel 718: a crystal plasticity modelling approach

Authors: Wenye Ye; Pankaj Kumar; Leslie T. Mushongera

Addresses: Department of Chemical and Materials Engineering, University of Nevada, 1644 N. Virginia Street, Reno, NV, 87557, USA ' Department of Mechanical Engineering, University of New Mexico, 1, MSC01 1150, Albuquerque, NM 87131, New Mexico, USA ' Department of Chemical and Materials Engineering, University of Nevada, 1644 N. Virginia Street, Reno, NV, 87557, USA

Abstract: Additive manufacturing provides an opportunity to manufacture complex geometry components of Inconel 718 efficiently. However, it is essential to develop an understanding of microstructure dependent fatigue to ensure the safety of these components in applications. The various microstructure constituents affect the fatigue performance. Among various microstructure constituents, the grain morphology is known to significantly affect fatigue performance. In the present study, a rigorous analysis of the microstructure effect considering the typical columnar (as-built) and equiaxed (annealed) grain on the fatigue behaviour has been studied using crystal plasticity modelling. The analysis indicated that at low cycles, the fatigue performance of columnar microstructure is better than the equiaxed microstructure. On the other hand, the equiaxed microstructure at higher cycles shows higher fatigue performance than the columnar morphology. Stress relaxation due to local plastic deformation in both the columnar and equiaxed grain microstructure plays a role in delaying crack initiation during cyclic loading.

Keywords: Inconel 718; additive manufacturing; fatigue; cyclic stress-strain loops; crystal plasticity.

DOI: 10.1504/IJTAMM.2021.120798

International Journal of Theoretical and Applied Multiscale Mechanics, 2021 Vol.3 No.4, pp.313 - 328

Received: 06 Mar 2021
Accepted: 03 Sep 2021
Published online: 08 Feb 2022 *