Additive Manufacturing for Energy Applications II: Characterization I
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Isabella Van Rooyen, Pacific Northwest National Laboratory; Subhashish Meher, Pacific Northwest National Laboratory; Indrajit Charit, University of Idaho; Michael Kirka, Oak Ridge National Laboratory
Wednesday 8:30 AM
February 26, 2020
Room: 9
Location: San Diego Convention Ctr
Session Chair: Subhashish Meher, Idaho National Laboratory; Bharat Gwalani, Pacific Northwest National Laboratory
8:30 AM Invited
Influence of Prior EBM Alloy 718 Microstructure on Build Properties after Varied Thermal Post-treatments: Sneha Goel1; Johannes Gårdstam2; Jonas Olsson1; Uta Klement3; Shrikant Joshi1; 1University West; 2Quintus Technologies AB; 3Chalmers University of Technology
Additive manufacturing by electron beam melting (EBM) has gained rapid popularity for layer-by-layer fabrication of complexly shaped parts with difficult-to-machine materials. The workhorse superalloy Alloy 718, widely used in the aerospace industry for gas turbine applications, is one such material that has garnered significant attention for AM processing. Notwithstanding the considerable progress in improving AM processes, suitable thermal post-treatments involving heat treatment and/or hot isostatic pressing (HIP) are being sought to make AM-built parts suited for demanding applications. Consequently, the effect of post-treatments on microstructure and properties of EBM-built Alloy 718 needs to be understood. The presentation will focus on the response of EBM Alloy 718 builds with vastly varying as-built microstructures (equiaxed-columnar, dense-porous) to HIPing, solutionizing and aging. Illustrative results highlighting the influence of post-treatments on defect content, grain morphology/size, phase constitution, hardness, etc. will be presented, with particular emphasis on role of as-built microstructure on final part properties.
8:50 AM
Mechanical and Thermal Properties of Electron Beam Melting Additively Manufactured Tungsten for Fusion Energy Applications: John Echols1; Lauren Garrison1; Elizabeth Ellis1; Yutai Katoh1; Michael Kirck1; Ryan Dehoff1; Timothy Horn2; Christopher Rock2; Christopher Ledford2; Sillivan Figurskey2; 1Oak Ridge National Laboratory; 2North Carolina State University
The plasma-facing components (PFCs) of fusion reactors will be composed of vast numbers of small pieces that require varied shaping, internal channels, and dissimilar material joints. Among other specifications, PFCs must have high thermal conductivity and melting temperatures. Tungsten has attractive materials properties for this application, but due to its high melting point and brittleness at room temperature, it is difficult to fabricate by traditional means into the necessary small parts and complex geometries. Electron beam melting (EBM) provides a useful avenue to part manufacture. However, a working understanding of the change to fusion-relevant mechanical properties and their relationship with microstructure with respect to current technologies and techniques with EBM must be established. This study investigates fusion-relevant mechanical properties of bulk EBM prints including tensile, thermal conductivity, hardness, roughness, and density. The results are evaluated against microstructure and compared to properties of traditionally manufactured tungsten.
9:10 AM
Mechanical Testing of 3D Printed Materials: Nicole Wagner1; Dika Handayani1; Victor Okhuysen1; Kyle Garibaldi1; Michael Seitz1; 1California State Polytechnic University, Pomona
Fused deposition modeling (FDM) has been a rapidly growing 3D printing technology for polymer-based products. Additive manufacturing technologies have seen an expansion into printing various polymers, including acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) on various printers and print orientations. In this study, we evaluate the tensile strength characteristics of FDM printed ABS and PLA parts. Specimens with a dog bone geometry were printed on both an entry-level FlashForge 3D printer and a Stratasys F170, using the ASTM D638 standard test method. A flat build orientation was used with varying raster orientations of 0, 45 or 90 degrees on the build plate. An Instron Tensile Testing machine was used to evaluate the stress-strain characteristics of each specimen and determine yield and tensile strength of the parts. Results showed that there was a negligible effect on the strength of the material for the different raster orientations.
9:30 AM
Study Of Transition In Mechanical Properties Of A356/316L Additively Manufactured Interpenetrating Phase Composites: Jiahao Cheng1; Xiaohua Hu1; Maxim Gussev1; Derek Splitter1; Amit Shyam1; 1Oak Ridge National Laboratory
A356/316L interpenetrating phase composites, fabricated by infiltrating additively-manufactured 316L lattices with molten A356, have shown diverse mechanical properties that are controllable by adjusting volume-fraction and/or topology of 316L reinforcement. Under uniaxial tension, the composites with 40 vol% 316L showed two times higher ductility and tensile-strength compared to the 20 vol% 316L sample at the cost of 27% density increase. Transition from localized deformation and fracture to delocalized damage is observed from 20 vol% to 40 vol% 316L, accompanied with four times increase in energy absorption capacity. This transition makes possible the fabrication of hybrid structural components of tailored properties and weight by printing spatially varying 316L reinforcement. Finite-element analysis was conducted and compared to in-situ digital image correlation to study the mechanism dominating evolution of properties. Inspection of specimens suggested that exceptional damage tolerance is a result of interpenetrating structure. The influence of interface-bonding and altering lattice-structure will be discussed.
9:50 AM Break
10:10 AM
Microstructural Characterization and Thermomechanical Behavior of Additively Manufactured AlSi10Mg Material and Architected Cellular Structures: Alya Alhammadi1; Kamran Khan1; Oraib Al-Ketan1; Mohamed Hassan1; Reza Rowshan2; Rashid Abu Al-Rub1; 1Khalifa University of Science and Technology; 2New York University - Abu Dhabi
There is increasing interest in new types of architected-metallic-cellular-structures for various applications due to advances in metallic-additive-manufacturing technologies. In this work, the microstructure- and mechanical-properties of additively-manufactured AlSi10Mg TPMS-sheet-based cellular-structures are studied. The tensile-coupons of base-material are fabricated using laser-powder-bed-infusion 3D-printing technique in three different printing-directions, XY-XZ-Z. Tests are carriedout at 25-200°C, coupons undergo a stress-relieving heat-treatment prior to testing which was shown through EBSD-maps to result in grain-growth and more ductile-behavior. It is seen that tensile-strength decreases with temperature increase that is associated with significant increase in elongation at fracture. Diamond TPMS-structures are also 3D-printed at four relative-density values and the morphology is studied through scanning-electron-microscopy and X-ray computed-tomography. The diamond TPMS-structures undergo compression-tests at 25°C-150°C. The maximum-strength, yield-stress, and Young-modulus increase with the increase in relative-density while the fracture-strain remains almost constant. The results show that AlSi10Mg Diamond TPMS-cellular-structures have excellent mechanical-properties making them ideal for lightweight-strong-structural systems.
10:30 AM
Microstructure of the Ferritic-martensitic Steels From Simulated Additive Manufacturing Heat Treatment: Weicheng Zhong1; Lizhen Tan1; Kevin Field2; Niyanth Sridharan1; Ying Yang1; Kurt Terrani1; 1Oak Ridge National Laboratory; 2University of Michigan, Ann Arbor
Direct energy deposition that is one form of additive manufacturing (AM) is being developed to produce ferritic-martensitic (FM) steel components for nuclear applications. In this study, a cyclic heat treatment that simulates AM processing was applied to three new FM steels using a dynamic thermal-mechanical simulator system, including Fe-11Cr-2Mn, Fe-9Cr-4Mn, and Fe-10Cr-2Mn with minor V, Ta, and W additions. The goal of the work is to understand and compare the microstructures of the FM steels subjected to the same simulated AM heat treatment. The steels demonstrated mostly lath structure with some heterogeneous grains/domains. Transmission electron microscopy revealed V/Ta-rich MX and M23C6 precipitates with densities on the order of 1021 and 1020 m-3, respectively, in the Fe-11Cr-2Mn and Fe-9Cr-4Mn. In contrast to conventional FM steels, M23C6 with an average size of 30-35 nm was observed mostly within grains. On the other hands, no M23C6 or MX precipitate was observed in Fe-10Cr-2Mn.
10:50 AM
Tailoring Laser Direct Deposited High Purity Alumina Ceramics via Dopants: John Pappas1; Aditya Thakur1; Xiangyang Dong1; 1Missouri University of Science and Technology
Laser direction deposition provides a promising method in printing ceramics but poses great challenges in controlling properties due to prevalent cracking issues. In this paper, a systematic study was performed on the effects of processing conditions and compositions on as-fabricated part density, grain size and distribution, crack prevalence and characteristics, and mechanical properties. In particular, doping with different weight percentages of zirconia was found to be an efficient way of controlling microstructure, densification, and cracking. Near fully dense alumina ceramics were successfully fabricated. Zirconia, segregated into grain boundaries, helped toughen the deposited ceramic samples through crack inhibition and suppression. Increased dopants resulted in grain refinement, which was correlated with the fracture strength of the fabricated specimens. The dopants, in combination of controlled high cooling rates, was demonstrated with promising results in controlling cracking issues inherent in laser direct deposition of ceramics and tailoring their mechanical strength.
11:10 AM
Additive Manufacturing of YSZ Ceramics by Laser Engineered Net Shaping: Xueliang Yan1; Yan Chen2; Fei Wang1; Cody Kanger1; Michael Sealy1; Bai Cui1; 1University of Nebraska-Lincoln; 2Oak Ridge National Laboratory
Compared to metals, laser additive manufacturing of ceramic materials is more challenging because of the intrinsic brittleness of ceramics and the high temperature gradients, which can induce significant defects and cracking. This presentation shows our novel research on the successful additive manufacturing of yttria–stabilized zirconia (YSZ) ceramics by a laser engineered net shaping (LENS) process. The microstructure formation, such as phase composition, grain size, and crack density, has been carefully characterized by neutron diffraction and electron microscopy, which are correlated with the LENS conditions such as the laser power. Phase transformation from monoclinic to tetragonal/cubic occurred during the LENS of YSZ ceramics. The crack density inside the manufactured parts was reduced at a higher laser power.