Additive Manufacturing: Nano/Micro-mechanics and Length-scale Phenomena: On-Demand Oral Presentations
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Meysam Haghshenas, University of Toledo; Robert Lancaster, Swansea University; Andrew Birnbaum, Us Naval Research Laboratory; Jordan Weaver, National Institute Of Standards And Technology; Aeriel Murphy-Leonard, Ohio State University
Monday 8:00 AM
March 14, 2022
Room: Additive Technologies
Location: On-Demand Room
Mechanical Properties of Single Struts Made by Laser Powder-bed Fusion: Effects of Melt-track Transient States and Process Parameters: Ben Fotovvati1; Subin Shrestha1; Kevin Chou1; 1University of Louisville
Porous metal structures are composed of several single struts, properties of which influence the properties of the whole structure. Layer-by-layer fabrication of porous structures requires very short laser scan tracks. The available literature correlates the laser powder bed fusion (LPBF) process parameters to parts mechanical properties, however, in porous structures that contain small features, a different phenomenon is governing these correlations. Our previous research studies indicate that the melt-pool does not reach a quasi-steady state in short scan tracks. Having consistent melt-pool dimensions is particularly crucial for small features, such as single struts. The transient length, i.e., the length at which the melt-pool reaches a steady-state, strongly depends on the LPBF process parameters. In this work, small tensile samples, with gauge widths ranging from 0.25 mm to 2.0 mm, are fabricated using different process parameters to investigate the effect of transient length on the mechanical properties of single struts.
Designing Additive Layered Manufacturing Inspired Damage Tolerant Architectures: Deepesh Yadav1; Tanmayee More1; B N Jaya1; 1Indian Institute of Technology Bombay
Thermal spray is a form of additive manufacturing of materials in which porosities occur due to gas entrapment or inter-splat cracks. The effect of porosity and its distribution (in terms of size, morphology, location) as inspired by thermal spray coating microstructures, on damage tolerance has been investigated. Globular and ellipsoidal features were micro-machined in a brittle Poly(methyl methacrylate) polymer, with the objective to optimize the size and arrangements of features for best damage tolerance. Damage tolerance was determined in terms of work of fracture under three-point bend loading. The energy release rate around the features was calculated using micro-mechanics-based numerical modeling for different sizes and arrangements. Rate of increase in energy release rate is more in globular-like feature than ellipsoidal feature. Globular features gave better damage tolerance in terms of initiation fracture toughness compare to ellipsoidal, but ellipsoidal offered more resistance to crack propagation and better overall damage tolerance.
Cancelled
The Role of Microstructure on the Creep Response of Additively Manufactured IN718 Using Crystal Plasticity: Veerappan Prithivirajan1; M Arul Kumar1; Laurent Capolungo1; 1Los Alamos National Lab
Additive manufacturing (AM) has garnered significant interest as it offers many advantages over the conventional techniques. AM also causes drastic variability in the microstructure, which controls the creep performance and rupture of the material, a common mode of failure under high temperature loading conditions. It is therefore necessary to understand the role of microstructure on the creep response to accelerate the certification of the AM material. The material of interest in this work is the AM Inconel 718 (IN 718), a high temperature Ni-based superalloy. In this study, we investigate the role of different microstructures (equiaxed and columnar) on the creep response of AM IN718 using a full-field fast Fourier transform based crystal plasticity model that accounts for dislocation glide, dislocation climb, and diffusion processes. We then compare our predictions with the experimental results.
Correlating the Microstructure and Mechanical Properties of Additively Manufactured Al-Ce Alloys Using In-situ Micromechanical Testing: Tanvi Ajantiwalay1; Richard Michie2; Amit Shyam2; Alex Plotkowski2; Arun Devaraj1; 1Pacific Northwest National Laboratory; 2Oak Ridge National Laboratory
Al-Ce based alloys are current candidates for high-temperature applications due to their excellent thermal stability and good castability. One of the techniques useful in processing these alloys is the laser powder bed fusion (LPBF) based additive manufacturing (AM) which, is shown to be beneficial to modify its eutectic microstructure. Some heterogeneity however, with the formation of melt pool boundaries (MPBs) is observed in the microstructure which are known to be the weak sites during bulk-scale mechanical testing. Thus, to improve an understanding of the local mechanical properties within MPBs and to further optimize the LPBF process we performed in-situ nanoindentation and micro-pillar compression using the PI89 Picoindenter at room and high temperatures. The results obtained from this study in the form of load vs. displacement curves are then used to calculate material properties such as hardness, yield stress and elastic modulus.
Three-pronged Approach to Prediction of Polymer-additive System Rheology: Scott Muller1; Peiyuan Gao1; Lirong Zhong1; Amanda Howard1; Jaehun Chun1; Gregory Schenter1; 1Pacific Northwest National Laboratory
The inclusion of molecular additives gives an extra layer of customization to 3D-printed polymers. Additives may also affect, and be affected by, the rheological properties of a polymer melt. This research seeks to develop a mechanistic understanding of dispersion of functional additives and their effect on the rheological properties under shearing relevant to 3D-printing processes. The approach is threefold: (1) experimental rheometry measurements, (2) coarse-grained simulations, and (3) uniting of measurements and simulations into a physics-informed neural network model. This approach links structural behavior at the molecular scale to experimental observations at the macroscopic scale and provides predictive capability. The additive considered is tetraphenylethylene, a mechanochromic molecule which exhibits aggregation-induced-emission (i.e., its fluorescence changes depending on its degree of dispersion). The considered polymer matrix is polyetherketoneketone, a high-performance semi-crystalline thermoplastic.
Mechanical Response of “Meta-Polycrystalline” Steel 316L Produced by Laser Powder Bed Fusion: Karl Sofinowski1; Mallory Wittwer1; Matteo Seita1; 1Nanyang Technological University
Additive manufacturing has made it possible to create materials with site-specific microstructures down to the micron scale. This new paradigm enables the design of advanced metal alloys with tailored mechanical properties and improved performance. Here, we use laser powder bed fusion to produce samples of stainless steel 316L with site-specific crystallographic textures by manipulating the local solidification conditions across the build. We use this strategy to design samples of quasi-single crystal blocks with controlled shape, size, an orientation. These “meta-polycrystals” can mimic grain-scale structures such as curved grain boundaries, twin boundaries, and triple junctions. We perform various mechanical tests on the meta-polycrystals to probe the effect of the interface misorientation and curvature on the deformation. Using in situ digital image correlation and directional reflectance microscopy, we measure the strain evolution and crystallographic rotation of these structures. We then compare the mechanical response against that of single crystals and polycrystals.
The Effect of Defects on Additive Manufacturing Material at the Microscale -- Approaches to Manage the Consequences: Martin White1; Mohsen Seifi1; 1ASTM International
At the microscale, material produced by Additive Manufacturing inherently contains ‘artifacts’ or ‘defects’, such as porosity or lack of fusion. This presentation will give detail on the effect of these features, linking the microscale behaviors to Structural Integrity considerations such as mechanical properties, safety classifications, and how to control variability in the processes. Relevant ASTM Standards will be covered, as well as how to use Standards to enable the testing and inspection at the microscale.Finally, insight for strategies to prevent, identify, and manage these challenges will be shared, based on experiences from the author, and ongoing work within the ASTM Additive Manufacturing Center of Excellence.
Indentation-derived Mechanical Properties of Ti-6Al-2Sn-4Zr-2Mo Alloy Fabricated through Laser-powder Bed Fusion: Harish Kaushik1; Meysam Haghshenas2; Amir Hadadzadeh1; 1University of Memphis; 2University of Toledo
T-6Al-2Sn-4Zr-2Mo (Ti6242) is a near-α titanium alloy, suitable for high-temperature applications. Unlike the conventional α+β Ti-6Al-4V (Ti64), with applications below 400°C, Ti6242 can be readily used in high temperatures up to 540°C. Ti6242 has been conventionally manufactured through casting and forging techniques. The emergence of additive manufacturing (AM) processes as revolutionary manufacturing techniques makes it imperative to study the fabrication of Ti6242 through AM processes. In the current study, Ti6242 samples were fabricated through the laser powder bed fusion (L-PBF) process with different process parameters. The micromechanical properties (e.g., indentation hardness, plasticity index, wear index, reduced modulus) of the as-built and heat-treated L-PBF-Ti6242 were evaluated using a depth-sensing indentation testing technique. The results were compared to the L-PBF-Ti64 counterparts to draw a perspective on the effect of material composition on the micromechanical properties.