Quantifying Microstructure Heterogeneity for Qualification of Additively Manufactured Materials: Characterization of Heterogeneity
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Phase Transformations Committee, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Sharniece Holland, Washington University in St. Louis; Eric Payton, University of Cincinnati; Edwin Schwalbach, Air Force Research Labroatory; Joy Gockel, Colorado School Of Mines; Ashley Paz y Puente, University of Cincinnati; Paul Wilson, The Boeing Company; Amit Verma, Lawrence Livermore National Laboratory; Sriram Vijayan, Michigan Technological University; Jake Benzing, National Institute of Standards and Technology
Thursday 2:00 PM
March 23, 2023
Room: 24B
Location: SDCC
Session Chair: Ashley E. Paz y Puente, University of Cincinnati; Paul Wilson, Boeing
2:00 PM Invited
In Situ Monitoring of Recrystallization during Laser Powder Bed Fusion of 316L Stainless Steel by Means of Synchrotron X-ray Diffraction: Claire Navarre1; Milad Hamidi1; Reza Esmaeilzadeh1; Charlotte de Formanoir1; Lucas Schlenger1; Steven van Petegem2; Nicola Casati3; Roland Logé1; 1École polytechnique fédérale de Lausanne (EPFL), Switzerland / Laboratory of Thermomechanical Metallurgy (LMTM); 2Structure and Mechanics of Advanced Materials Group (SMAM), Paul Scherrer Institut (PSI), Switzerland; 3Swiss Light Source (SLS), Paul Scherrer Institut (PSI), Switzerland
Laser Powder-Bed Fusion (LPBF) is an Additive Manufacturing process based on layer-by-layer selective melting and solidification of metallic powders. While LPBF allows fabricating highly dense and complex parts, it suffers from unrepeatability of generated microstructures. Accordingly, an online monitoring system able to identify the occurrence of specific events is being developed, through in situ synchrotron X-Ray Diffraction (XRD). The kinetics of fast recrystallization during both LPBF and subsequent operando laser heat treatments is investigated in 316L, by looking at the evolution of XRD peak narrowing over time. The influence of dislocation density on the recrystallization kinetics is quantified by performing these laser treatments on a cold-rolled 316L plate and an LPBF 316L sample. The latter is treated by Laser Shock Peening in order to increase the dislocation content. Contributions from grain size and dislocation density are analyzed and linked to EBSD maps of the recrystallized microstructures.
2:25 PM
Large-scale Image Analysis of Melt Pools in Complex Additively Manufactured Artifacts: Guangyu Hu1; Hunter Taylor2; Ryan Wicker2; Marat Latypov1; 1University of Arizona; 2University of Texas at El Paso
Investigation of melt pools can provide insights into the complex heat transfer and solidification phenomena that determine the microstructure and properties of additively manufactured metal parts. In this work, we carry out large-scale image processing and computer vision of optical images of metallographic sections from complex 3D printed artifacts. We first identify melt pools in the images and then investigate their spatially resolved size and morphology distributions. Statistical description of melt pool size and morphology as well as their heterogeneities provides quantitative foundation for establishing relationships with part geometry, microstructure, and in situ monitored process data. The results can also serve as a valuable dataset for qualification efforts as well as calibration and verification of multiphysics models for metal additive manufacturing.
2:45 PM
Heterogeneous Microstructure and Location-specific Mechanical Performance of Ti-6Al-4V Parts Made by Laser Directed Energy Deposition: Janelle Hobbs1; Xiaochuan Tang1; Kaka Ma1; 1Colorado State University
Heterogeneity and texture in microstructure have become commonly known phenomena in additively manufactured metals and alloys, due to the transient heat transfer conditions of the layer-by-layer deposition. Particularly, Ti-6Al-4V, a duplex α-β alloy, can exhibit distinctive and varying microstructure at different locations in the printed parts. In the present study, Ti-6Al-4V tubes are made by laser directed energy deposition. The distribution and relative amount of Widmanstätten microstructure and martensitic features are quantified as the location moves from bottom to top along the build direction and from inner wall to outer wall along transverse direction. Location-specific mechanical performance is measured via nanoindentation and nanoscratch. Uncertainty analysis is applied to identify appropriate weighting factors to various laser scanning parameters. Based on those data, we propose a strategy of intra- and inter-layer modification of laser power and hatch parameters with the assistance of in-situ melt pool monitoring to improve microstructural homogeneity.
3:05 PM
Correlative Modeling of Laser Powder Bed Fusion Surface Characteristics to Internal Defects: Sean Dobson1; Ashely Paz y Puente1; 1University of Cincinnati
Laser powder bed fusion (L-PBF) additive manufacturing (AM) continues to find application in industries like medical and aerospace. As AM pushes into use for critical parts, reliable methods, such as in-process monitoring, will need to be devised to ensure part quality. Some in-process monitoring uses surface roughness; however, it is often only a metric for recoater health. This on-going work demonstrates the potential for such a method, by developing a correlative model of surface features to internal defect quantity and type, and even microstructural characteristics. Surface, porosity, and microstructure were characterized using high resolution 2-D and 3-D methods. Preliminary findings demonstrate a deep fundamental connection between internal and external defects. The final results of this endeavor will lay the foundation for the development of a novel in-process monitoring system employing deep learning.
3:25 PM Break
3:40 PM
Characterization of Titanium Additions in Selectively Laser Melted High-strength Aluminum Alloy by Correlative X-ray and Electron Microscopy: Daniel Sinclair1; Nikhilesh Chawla1; Amey Luktuke1; 1Purdue University
Selective laser melting (SLM) has received significant attention as a transformative metal 3D printing method in commercial, industrial, and defense applications. The SLM of aluminum parts extends weight reduction benefits; however, the cracking susceptibility of age-hardened aluminum alloys makes them unsuitable for structural components. To minimize cracking, grain refining additives are being developed. For example, the reactive additive manufacturing (RAM) process, developed by Elementum 3D, introduces titanium particles which react with aluminum to form refining intermetallics. Using x-ray microscopy, the size distributions of titanium particles in an SLM AA7050-RAM alloy were measured before and after SLM. Additionally, melted and un-melted particles were identified by automated measurement and classification, enabling a three-dimensional assessment of melt pool heterogeneity. Tomography results were further related to microscopy and nanoindentation of melted and un-melted titanium particles. The influence of particle melting and distribution on manufacturing and mechanical properties was studied and will be discussed.
4:00 PM
Use of Profilometry-based Indentation Plastometry (PIP) to Study Inhomogeneities in Additively Manufactured Components: Max Burley1; Jimmy Campbell1; Gael Guetard2; Charlie Pearson2; Becky Reiff-Musgrove1; Wenchen Gu1; Bill Clyne1; 1Plastometrex Ltd; 2Alloyed
The PIP procedure (https://doi.org/10.1002/adem.202100437) is now a mainstream mechanical test. Products are available in which indentation, profilometry and data processing are all automated and take about 3 minutes. It allows stress-strain curves to be obtained for relatively small volumes of material, such that local properties can be mapped where they are changing over short distances. It has been used to measure local property variations in the vicinity of welds (https://doi.org/10.1002/adem.202101645). It can also be used to detect and characterize anisotropy, for example in AM superalloy components (https://doi.org/10.2139/ssrn.3746800). In the current work, PIP is applied to a relatively large and complex AM component, in which the growth conditions, and hence the mechanical properties, vary with location during production. It is shown that these consequent variations can be detected and characterized on a scale of a few mm. The procedure has also been applied to study the anisotropy developed in this component.