Additive Manufacturing: Advanced Characterization with Synchrotron, Neutron, and In Situ Laboratory-scale Techniques II: Advanced Mechanical Characterization of AM Alloys
Sponsored by: TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Fan Zhang, National Institute of Standards and Technology; Donald Brown, Los Alamos National Laboratory; Andrew Chuang, Argonne National Laboratory; Joy Gockel, Colorado School of Mines; Sneha Prabha Narra, Carnegie Mellon University; Tao Sun, University of Virginia

Thursday 8:30 AM
March 3, 2022
Room: 258A
Location: Anaheim Convention Center

Session Chair: Donald Brown, Los Alamos National Laboratory

8:30 AM  
In Situ Synchrotron Characterization of the Fatigue Behavior of WE43 Mg Porous Scaffolds for Biomedical Applications: Dolores Martín1; Guillermo Domínguez1; Muzi Li1; Federico Sket1; Monica Echeverry-Rendón1; Felix Benn2; Alexander Kopp2; Jon Molina-Aldareguía1; Javier Llorca3; 1IMDEA Materials Institute; 2Meotec; 3IMDEA Materials Institute & Technical University of Madrid
    Porous cubic scaffolds of 10 x 10 x 10 mm3 of WE43 Mg alloy with different lattice structure and an average strut diameter of 500 µm were manufactured by laser powder bed fusion. They were surface modified by plasma electrolytic oxidation to improve the corrosion resistance and biocompatibility. The fatigue life was determined by means of ex situ tests under stress control in compression/compression fatigue with a stress ratio Smin/Smax= 0.1 for different values of the maximum load in as-printed scaffolds or after immersion in simulated body fluid. Additionally, in situ synchrotron X-ray microtomography compression tests were carried out in as-printed scaffolds and after immersion in simulated body fluid. The results of the mechanical tests, together with the microstructural observations, provided new insights on the deformation and fracture mechanisms of porous Mg scaffolds under static and cyclic load after immersion in simulated body fluid.

8:50 AM  
Investigating the Impact and Evolution Porosity of LPBF Ti6Al4V Using In-situ Mechanical/XCT Testing: Hossein Talebinezhad1; Ralf Fischer1; Barton Prorok1; David Hertz-Eichenrode1; 1Auburn University
    The evaluation of pores under tensile and torsion loads of LPBF Ti6Al4V was carried out in situ with an X-ray CT. The printing parameters were varied to achieve different degrees of porosity and as-printed samples were heat-treated between 600-900°C at various times to modulate microstructure. The in-situ mechanical testing in the X-ray CT was performed to enable imaging and evolution of defects that led to failure. The XCT defect analysis was performed at individual stages of applied load on both as-built and heat-treated samples. Under different sample strains, the mean diameter, density, volume fraction and sphericity of pores were quantified. The results are aimed to impact the use of LPBF Ti6Al4V in medical and other applications where mechanical performance is critical.

9:10 AM  
Cellular Structures Strengthening Mechanisms and Thermal Stability of L-PBF Stainless Steel 316L: Jean-Baptiste Forien1; Aurelien Perron1; Sylvie Aubry1; Nicolas Bertin1; Amit Samanta1; Alexander Baker1; Y. Morris Wang1; Marissa Linne1; Margaret Wu1; Nathan Barton1; Thomas Voisin1; 1Lawrence Livermore National Laboratory
     In this work, we investigate the deformation mechanisms and thermal stability of L-PBF 316L SS. Our main results show that the high density of entangled dislocations inside cell walls have a higher tendency to dissociate, forming wider stacking faults while many oxide precipitates are confined inside cell walls. Both features act as barriers to moving dislocations upon plastic deformation and contribute to the high strength. Our dislocation dynamic simulations indicate that segregated particles are effective in blocking dislocations locally, helping the formation of dislocation cells and participating to the material strengthening. Our characterizations using electron microscopy, in situ synchrotron X-ray diffraction, CALPHAD simulations, and tensile testing of post-processed annealed materials reveal three heat treatment zones between 600 and 1200oC where the structure-property relationship can be tuned. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

9:30 AM  
On the Effects of Additive Manufacturing Process Parameters on the Performance of Hastelloy-X: A Neutron Diffraction Experiment and CPFE Modeling: Ahmed Aburakhia1; Ali Bonakdar2; Marjan Molavi-Zarandi3; Joe Keller4; Hamidreza Abdolvand1; 1Western University; 2Siemens Energy Canada Limited; 3National Research Council ; 4ISIS Neutron and Muon Source User Office
    Additive manufacturing (AM) has provided industry with the design flexibility to build mechanical parts with complex geometries to improve materials performance. However, understanding the influence of AM process parameters on the manufactured parts is challenging. A series of uniaxial neutron diffraction compression experiments were conducted on Hastelloy-X, to understand lattice strains evolution and how they are affected by changing the AM process parameters. Electron Backscatter Diffraction measurements were also conducted to characterize the initial texture of the samples. The measured microstructures are imported into a crystal plasticity finite element model to understand the active deformation modes. Results suggest that the specific energy input (SE = p / vd) has an influence on the AM-built parts, where p is the laser power, v is the scanning speed and d is the hatch spacing. Columnar grains with textured material are observed at higher SE, while random texture is observed at lower SE.

9:50 AM Break

10:05 AM  
In-situ Process Monitoring for Laser Powder Bed Fusion: A Data-driven Approach: Anant Raj1; Dongli Huang1; Benjamin Stegman1; Hany Abdel-Khalik1; Xinghang Zhang1; John Sutherland1; 1Purdue University
    The critical issue of part-to-part repeatability continues to impede large-scale adoption of additive manufacturing beyond rapid prototyping. A wide variety of in-situ monitoring techniques have been developed to address this issue. For laser powder bed fusion, co-axial melt-pool monitoring is one of the most widely used techniques that provides direct access to the quality of the melt-pool. However, an extensive quantitative analysis of the variation of the in-situ melt-pool signatures based on print parameters and process fluctuations and their impact on the final part quality has yet to be undertaken. In this study, we employ supervised and unsupervised machine learning to demonstrate that the in-situ melt-pool signatures can be distinctly mapped onto corresponding print parameters along with process fluctuations like variation across the build-plate. Further, our analysis suggests that in-situ signatures can be leveraged to predict the mechanical properties of the part, enabling development of control algorithms for better repeatability.

10:25 AM  
In-situ Residual Strain Monitoring in Metal Additive Manufacturing: Sandra Cabeza Sanchez1; Burak Ozcan1; Thilo Pirling1; Thomas Hansen1; Ines Puente Orench2; 1ILL; 2ILL, CSIC
     The mechanical performance of Metal Additive Manufacturing (MAM) components is potentially affected by complex gradients of residual stresses in 3D. These initial state would evolve in jet unknown trends under in-operando conditions. Therefore, AM structural components require the implementation of new characterization approaches towards their safe application. Neutron strain diffraction enhances mapping of the full strain tensor within the bulk of polycrystalline materials. This non-destructive technique allows the investigation of complete development cycles on a same sample and also in-situ/operando investigations.MAM research at SALSA (Stress Analyser for Large Scale engineering Applications) will be presented encompassing critical aspects in residual stress analysis: strain monitoring during direct energy deposition, influence of the scanning strategy, the non- symmetrical nature stress fields with respect to the geometry and the rotation of principal stress directions. A broad overview of reference d0 for strain-stress calculation is discussed between neutron powder diffractometers.