Multi-Scale Synchrotron X-ray Diffraction of Welded and Additively Manufactured Components
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Authors
Ravkov, Lucas Andre
Date
2025-01-06
Type
thesis
Language
eng
Keyword
materials engineering , additive manufacturing , X-ray diffraction , Solidification , welding , microstructural characterization
Alternative Title
Abstract
Industrial components consist of complex geometries that require simulations to optimize and control stresses during loading. These simulations are reliant on knowledge of physical properties, microstructure, and loading conditions, with validation through mechanical testing. Advanced manufacturing techniques like laser powder bed fusion (LPBF) manufacturing create unique microstructures that must be considered during mechanical modeling to match real conditions. X-ray Diffraction Line Profile Analysis (DLPA) can be used to characterize microstructural defects such as dislocation density, dislocation character, and coherent scattering domain size, which are the focus of this thesis.
The present work is four-fold: First, a software tool, fitPyk, was developed for iterative fitting of large spectral datasets. Two studies then describe methodology for 2D mapping of microstructural defect parameters (dislocation density, dislocation character, and domain size) using synchrotron X-ray diffraction in welded and LPBF stainless steel 316L (SS316L), analyzed through fitPyk.
Berkovic nanohardness mapping of the welded SS316L was used to inform a combined Taylor Law/Hall-Petch model, predicting yield stress from dislocation density, coherent domain size, and base yield strength. Results showed a correlation (R^2=0.46) to a model where yield stress increases with the square root of dislocation density (ρ^(1⁄2)) and decreases with the inverse square root of the coherent domain size (D^(-1⁄2)). Fitting parameters for the model are K_ρ=1.47±0.09×10^(-5) MPa∙m for the contribution of dislocation density, K_D=3.84±0.57×10^(-2) MPa∙√m for the domain size effect, and σ_o=643.41±12.98 MPa for the base yield strength. This allows yield stress in welded SS316L to be determined from diffraction data.
Finally, a novel method for extracting defect parameters in LPBF Hastelloy X (HX) using DLPA is demonstrated. The average ρ was found to be 9.40±2.85×10^14 m^(-2), with 66±20 % of material consisting of cell interior and 34±20 % consisting of cell wall. These results can inform models for additive manufacturing (AM) materials and help analyze large diffraction datasets using fitPyk.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International