Session: 03-12-01: Testing and Characterization

Paper Number: 132992

132992 - A Crystal Plasticity Model to Study Stress Localization and Size-Dependent Tensile Properties of Additively Manufactured Nickle-Base Superalloy: Haynes 214™ at Elevated Temperature 

Microstructures found in additively manufactured (AM) components often display unique characteristics in contrast to those produced using conventional manufacturing processes. Generally, these differences stem from the specific thermal histories experienced at the local level during the additive manufacturing build process. Previous research has illustrated that the mechanical properties of AM thin-walled structures can experience significant variations in response to changes in wall thickness, and this variability is dependent on temperature. The impact of temperature on these variations becomes more pronounced, particularly at elevated temperatures. The goal of this research is to investigate the nature of this size effect on tensile properties, such as yield strength, strain hardening rate, and ductility, for AM HAYNES 214 particularly under conditions of elevated temperature (250°C and 450°C). To explore the size effect, thin-wall structures were fabricated using HAYNES 214 powder, with four different thicknesses: 1.0 mm, 1.5 mm, 2 mm, and 2.5 mm. To obtain the constitutive response, initially, we developed a robust approach to generate a representative volume element (RVE) for HAYNES 214. Commencing with electron backscattered diffraction (EBSD) images of sections, the technique generates distributions of various morphological and crystallographic parameters, such as grain sizes, texture, and twin fraction. The effectiveness of the entire methodology is confirmed through a successful comparison of different statistics derived from the simulated microstructures with the actual EBSD data. Subsequently, we employed the Crystal Plasticity Fast Fourier Transform (CPFFT) based spectral method and relying on the phenomenological hardening law. We have successfully established a correlation between the local stress analysis conducted at the grain level and the global mechanical behavior observed in experimental results. This comprehensive examination of stress and strain at the micro level has uncovered variations in mechanical properties that are directly linked to the thickness of the thin-wall structure. Additionally, we explored how the local stress state, influenced by grain neighborhood effects, contributes to the observed localization behavior. Variations in the arrangement and properties of neighboring grains can lead to different stress distributions at the micro level. We explored the factors that drive the non-uniform distribution of mechanical responses within the HAYNES 214 by addressing how the local stress state, influenced by these grain neighborhood effects, contributes to localization behavior. The manufacturing-induced plastic anisotropy in grain distribution discovered through this study opens avenues for future research. Specifically, it provides opportunities to modify the microstructural grain topology and solidification parameters, thereby influencing not only the mechanical behavior of thin-wall structures but also that of other load-bearing critical structures across various applications.

Presenting Author: Mohammad M. Keleshteri The University of Arizona

Presenting Author Biography: Mohammad, a postdoctoral researcher at the University of Arizona, specializes in computational mechanics. With prior experience as a Postdoctoral Fellow at the University of British Columbia, he concentrated on minimizing noise and vibrations in lattice structures. Currently, his focus lies in innovatively optimizing the topology and microstructure of lattice structures, contributing to advancements in the field.