Quantifying Microstructure Heterogeneity for Qualification of Additively Manufactured Materials: Quality Control, Data Analytics, and Modeling
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
Wednesday 8:30 AM
March 22, 2023
Room: 24B
Location: SDCC
Session Chair: Jake Benzing, National Institute of Standards and Technology; Sharniece Holland, Washington University in St. Louis
8:30 AM Invited
Opportunities & Challenges with Laser Powder Bed Fusion for Automotive Applications: Steel and Aluminum Alloys: Whitney Poling1; Andrew Bobel1; Md Ashabul Anam1; Mark Smith1; Tyson Brown1; Anil Sachdev1; 1General Motors, Global Research & Development
Metal additive manufacturing is a rapidly growing technology that offers many potential benefits to the automotive industry, such as functional prototyping, more design flexibility leading to light weighting and/or improvement in part performance, and the potential to reduce the cost and time associated with tooling for specific low volume part designs. Current challenges for implementing this technology for automotive manufacturing include expanding availability of automotive grade alloys, increasing throughput of machines, and controlling part quality, properties, and repeatability. This talk will focus on the development of GM custom aluminum and steel alloys for laser powder bed fusion systems. These alloys are designed to be low cost, tailored for AM processing, and applicable to a variety of vehicle applications. Microstructures and mechanical properties of samples built with these alloys will be discussed. The approach of minimizing post-processing to improve throughput will also be discussed.
8:55 AM
Microstructure and Mechanical Property Variations in Commercially Produced Laser Powder Bed Fusion 316L Stainless Steel: Jorge Ramirez Lujan1; Simon Richardsen1; Charles Smith1; Grant Zheng1; Garrison Hommer1; Jonah Klemm-Toole1; Steve Midson1; Xiaoli Zhang1; Amy Clarke1; Craig Brice1; Joy Gockel1; 1Colorado School of Mines
The austenitic stainless steel, 316L, is one of the most used steels in laser powder bed fusion (PBF-LB) additive manufacturing (AM). Accordingly, depending on where a PBF-LB part is made, there is a wide variety of equipment manufacturers and processing parameters used. As a result, a range of microstructures and mechanical properties are expected. In this presentation, variations and similarities in mechanical properties and microstructures from PBF-LB 316L builds are shown from four different commercial AM providers and different build geometries. By analyzing the compositions and processing parameters used in the builds, the mechanical behavior observed, and the requirements needed to transfer learned relationships from one machine to another are discussed. An understanding of the similarities and differences in the processing-structure-properties relationships from machine to machine will allow for a simplified qualification approach when expanding to suppliers using different PBF-LB machine technology.
9:15 AM
Long-term Process Stability in Laser Powder Bed Fusion: Michael Heiden1; Scott Jensen1; Jay Carroll1; Priya Pathare1; David Saiz1; Jonathan Pegues1; Bradley Jared2; Brad Boyce1; 1Sandia National Laboratories; 2University of Tennessee
While the geometric design freedom allowed by laser powder bed fusion (L-PBF) enables creation of complex parts with fine features, challenges associated with process qualification can deter wider adoption. Furthermore, a lack of historical performance data for statistical process control of witness coupons lowers confidence in the AM process. Here, we demonstrate long-term monitoring and variability assessment using small-featured (~1 mm) and larger material witness coupons. More than 550 tensile bars and 80 Charpy bars were built alongside various 316L L-PBF stainless steel parts to monitor tensile properties, density, hardness, and Charpy impact toughness. This collection of measurements was used to determine detectable property shifts correlated to L-PBF process changes. This study not only reveals the utility of monitoring process control via witness coupons but illustrates the sensitivity of different coupon types to detect L-PBF process changes.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
9:35 AM
Location Specific Characterization of Additively Manufactured Stainless Steel to Inform Build Data Analytics: Allyssa Bateman1; Christopher Snyder2; Scott Schier2; Ana Stevanovic2; Amanda Fernandez2; Elizabeth Sooby2; Brian Jaques1; 1Boise State University; 2University of Texas at San Antonio
Additive manufacturing (AM) could potentially produce nuclear reactor structural components with improved performance and decreased qualification time. However, micromechanical variability in AM parts can cause suboptimal micromechanical properties and chemical inhomogeneity. Data analytics shows the potential to predict defect probability and allow for in-situ part qualification, but requires significant amounts of training data. In this work, methods were developed to collect thousands of data points cataloguing location-specific microstructure, chemistry, mechanical properties and corrosion behavior across eighteen additively-manufactured stainless steel 316 parts. Wire EDM (electrical discharge machining) sectioned samples with minimal material loss while laser engraved scalebars and labels ensured precise location tracking. Characterization techniques included optical microscopy, scanning electron microscopy, x-rays, light element analysis, Raman spectroscopy, microhardness and steam oxidation. With this information, data analysts built methods to identify variances within data sets and connect trends in materials properties with original build parameters, improving future parts.
9:55 AM Break
10:20 AM
A Study of Microstructural and Mechanical Properties of 14YWT Oxide Dispersion Strengthened Steel Fabricated Using Laser Powder Bed Fusion Additive Manufacturing from Gas Atomized Reaction Synthesis Feedstock: Sourabh Saptarshi1; Matthew DeJong1; Chrisopher Rock1; Iver Anderson2; Ralph Napolitano3; Djamel Kaoumi1; Timothy Horn1; 1North Carolina State University; 2AMES Laboratory; 3Iowa State University
Laser powder bed fusion (LPBF) additive manufacturing (AM) is a promising route for the fabrication of oxide dispersion strengthened (ODS) steels. In this study, a 14YWT ferritic steel powder that was produced using a novel gas atomization reaction synthesis (GARS) method has been explored to fabricate intricately designed shapes and large prismatic blocks for feasibility and scalability. GARS powder bypasses the conventional mechanical alloying step typically required to produce ODS feedstock. Sub-sized tensile specimens have been harvested out of large blocks in various orientations from samples produced in varying powder chemistry, to analyze the effect of microstructural difference and powder chemistry on the mechanical properties of the samples.
10:40 AM
Control of Residual Stress and Distortion in Metal Additive Manufacturing via Inverse Mapping of Textures: Ruoqi Gao1; Hamid Garmestani1; Steven Liang1; 1Georgia Institute of Technology
The objective of this work is to develop a computational-mechanics texture-driven platform for predicting and controlling residual stress and part distortion in metal additive manufacturing (AM) via inverse mapping of microstructure in the fusion process parameter space. While previous studies on distortion issue have neglected the consideration of microstructure attributes, this work takes into account the effect of texture development and its gradient on residual stress by considering the anisotropic attributes of mechanical properties via crystal plasticity modeling. This work simulated the thermal deposition and temperature profiles of Ti-6Al-4V in a full-field closed-form solution for significant computational speed compared to numerically-iterative techniques. It will be followed by the prediction of texture development, texture-induced anisotropic mechanical properties, and residual stress considering materials property anisotropy. This work can further link the AM process parameters to microstructure and then to the final residual stress development and part distortion in explicit expression forms.
11:00 AM
Quantitative Analysis of Computed Tomography Characterization of Porosity in AM Ti64 Using Serial Sectioning Ground Truth: Bryce Jolley1; Christine Henry1; Michael Uchic1; Daniel Sparkman1; 1Air Force Research Laboratory
X-Ray Computed Tomography is widely-used for nondestructive characterization of porosity in Additively Manufactured parts. However, many factors can affect the accuracy of computer-based analysis of porosity from XCT data, including the XCT instrumentation settings, the choice of XCT reconstruction algorithms, and the segmentation and quantification metric(s) chosen. This presentation explores XCT porosity-characterization workflows for a 10 mm diameter cylindrical Ti-64 sample manufactured by laser powder bed fusion. The sample was characterized using four different XCT systems to explore the sensitivity to the XCT experimental, reconstruction, and segmentation workflows, after which automated serial sectioning was employed to estimate the true internal porosity distribution within a 2 mm thick subregion of the cylinder with ~2 micrometer spatial resolution. Notably, titanium alloy ball bearings were adhered to the sample (prior to XCT and serial sectioning characterization) to facilitate registration of the multi-modal datasets. Both global and local analysis of the porosity were made.
11:20 AM
X-ray Diffraction Peak Estimation Using In-Situ Melt-pool Sensors: Anant Raj1; Benjamin Stegman1; Charles Owen1; Hany Abdel-Khalik1; Xinghang Zhang1; John Sutherland1; 1Purdue University
Anisotropy inherent in the laser powder bed fusion (LPBF) process can lead to diverse microstructures with preferred grain orientations or texture. The texture impacts the properties of the printed parts and can be observed as the relative dominance of the different peaks in the x-ray diffraction. This work studies the x-ray diffraction profile across 100 IN718 tensile bars printed using a wide range of volumetric energy densities, based on a factorial design of experiment. The samples exhibited either (111) dominant, (200) dominant, or a mixed texture. The modulus of the samples was observed to be correlated to the relative intensity of the (111) and (200) peaks. Machine learning models are developed to predict the relative intensity of the peaks using co-axial melt pool area and intensity signatures. The models are expected to aid in part qualification, reducing the load on post-build testing.
11:40 AM
Synchrotron-based X-ray Microtomography Characterization of Solidification Cracks in Additively Manufactured IN738LC Alloy: Haoxiu Chen; Yu Zou1; 1University of Toronto
Additive manufacturing shows numerous unique advantages in the fabrication of complex nickel-based superalloy components. However, defect like solidification cracks is a major hindrance that impedes the further development of nickel-based superalloys in additive manufacturing technology seriously. Inconel 738LC samples were fabricated by laser powder bed fusion in different modes and investigated using a range of characterization techniques. Secondary electron microscopy and electron backscatter diffraction characterization confirm the solidification cracks. Synchrotron-based X-ray microtomography results reveal that from conduction mode to transition mode, the crack density increases four times, and the crack average thickness nearly doubled with the slight increase in the average crack length. The 3-dimensional data suggests that the larger plastic strain level leads to the formation of more cracks in the IN738LC alloy. This study reveals the critical mechanical factor affecting the cracking susceptibility of IN738LC and could be a guide for reducing solidification cracks in additive manufacturing.