Additive Manufacturing Fatigue and Fracture: Developing Predictive Capabilities: Reimagining Process, Material, and Component Optimization
Sponsored by: TMS Structural Materials Division, TMS: Additive Manufacturing Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Nik Hrabe, National Institute of Standards and Technology; John Lewandowski, Case Western Reserve University; Nima Shamsaei, Auburn University; Mohsen Seifi, ASTM International/Case Western Reserve University; Steve Daniewicz, University of Alabama

Tuesday 8:00 AM
March 1, 2022
Room: 258B
Location: Anaheim Convention Center

Session Chair: Nima Shamsaei, Auburn University

8:00 AM  Invited
Powder Oxygen Heterogeneities and Significant Intra-build Tensile Strength Variation from Common EB-PBF Ti-6Al-4V Powder Reuse Methods: Nicholas Derimow1; Jake Benzing1; Newell Moser1; Orion Kafka1; Nik Hrabe1; Priya Pathare2; Frank DelRio2; 1National Institute of Standards and Technology; 2Sandia National Laboratory
    Tensile strength was found to vary significantly (15% changes in UTS and YS) within a single build of electron beam powder bed fusion (EB-PBF) Ti-6Al-4V, and heterogenous local oxygen content was found to be the major contributor to this strength variability. No significant correlation was found between tensile behavior (375 specimens tested) and plate location (X-Y), build height (Z), porosity (x-ray CT, fractography), alpha lath thickness (SEM-BSE), or crystallographic texture (SEM-EBSD). Strength was found to correlate with local oxygen content (inert gas fusion, SEM-EDS/EPMA, and ICP-MS). Oxygen variation most likely arises from current EB-PBF Ti-6Al-4V powder reuse methods, which commonly involve frequent mixing of powders with differing oxygen content. Changes to powder reuse methodology to avoid significant differences in mechanical behavior for identical parts on the same build plate will be discussed. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

8:30 AM  
Characterization of Additively Manufactured 17-4 PH Steel Structure with Ultrasonic Technique: Justin Boswell1; Ping-Chuan Wang1; Aaron Nelson1; Terence Costigan2; Robert Van Pelt2; 1SUNY New Paltz; 2Sono-Tek Corporation
    Additive manufacturing (AM) of metal structures is rapidly gaining attention in the industry for convenient prototyping and fabrication of non-critical components that are otherwise impractical to produce. Many challenges remain before the technology becomes widely adopted. Primarily, AM parts tend to show weakness in mechanical integrity, mainly resulted from defects intrinsically associated with the AM process such as surface roughness, local delamination between printed layers, and lack of isotropic densification. An ultrasonic-based technique has been developed to characterize fatigue behavior of 17-4 PH stainless steel AM structure, revealing the strong dependence of fatigue lifetime on printing orientation. In this study, such dependence is further investigated and modeled to include the consideration of surface roughness and sintering condition, along with electron microscopy inspection of failed parts. The mechanism of fatigue failure in the steel AM specimens will be proposed and discussed in the presentation.

8:50 AM  
Fracture Behavior of Laser Powder Bed Fusion Fabricated Ti41Nb via In-situ Alloying: Sheng Huang1; Punit Kumar1; R. Lakshmi Narayan2; Wai Yee Yeong1; Upadrasta Ramamurty1; 1Nanyang Technological University; 2Indian Institute of Technology Delhi
    The investigation of the fracture behavior of Laser Powder Bed Fusion (LPBF) fabricated biocompatible β-Ti alloys is essential to enable their adoption as the next-generation biomedical implant materials. In our study, the fatigue crack growth (FCG) behavior and fracture toughness of in-situ alloyed Ti41Nb (wt.%) were explored. The inherently fast cooling rate of LPBF limited the melting and diffusion of Nb despite the utilization of optimized parameter, consequently led to the formation of layered mesostructure with alternated Nb deprived region and matrix region with close-to-nominal composition. Crack interactions with the mesostructure control the anisotropy in FCG and fracture toughness. The role of in-situ alloying in inducing toughening mechanism through mesostructure modifications and the future direction of in-situ alloyed β-Ti will be discussed in detail during the presentation.

9:10 AM  
Compression Testing and Characterization of L-PBF Ti-5Al-5V-5Mo-3C and E-PBF Ti-6Al-4V: Paul Korinko1; Mackenzie Smith1; 1Savannah River National Laboratory
    Titanium alloys are known for their high strength and lower density for use in aerospace applications. Ti-5Al-5V-5Mo-3C is a modern metastable beta titanium alloy that is being proposed for additive manufacturing (AM) development as an alternative to AM Ti-6Al-4V, an alpha + beta alloy. A study has been initiated to characterize the quasi-static compression behavior of these two alloys. The compression properties of Ti-6Al-4V fabricated by electron beam powder bed fusion in the as-AMed and heat treated conditions are being compared to the properties of laser powder bed fusion processed Ti-5Al-5V-5Mo-3C in the as-AMed, beta treated, and beta treated and aged conditions. Compression tests were conducted using digital image correlation (DIC) at various strain rates. The microstructures were characterized using optical and electron microscopy. The mechanical properties and microstructures will be discussed.

9:30 AM Break

9:50 AM  Invited
Rotating Bending Fatigue Behavior of EB-PBF Ti-6Al-4V with Globular Alpha Surface Layer: Nicholas Derimow1; Keenan Hanson2; Jake Benzing1; Newell Moser1; Orion Kafka1; Nik Hrabe1; 1National Institute of Standards and Technology; 2Stryker Orthopaedics
    A surface layer comprised of globular alpha has been identified in electron beam powder bed fusion (EB-PBF) titanium alloy (Ti-6Al-4V), and the effect of this surface layer on rotating bending fatigue behavior (ISO 1143) will be discussed during this talk. The globularization of alpha occurs due to post-build plastic deformation during normal sintered powder removal blasting, followed by standard Ti-6Al-4V hot isostatic pressing heat treatment. Three surface layer thickness conditions were studied by varying blasting working distance, i.e. the separation of the blasting nozzle from the part being blasted. An additional condition with no surface layer was studied by replacing blasting with ultrasonic techniques to remove powder. Microstructure (SEM-EBSD), porosity (x-ray CT), and surface roughness (optical profilometry) were characterized. The influence of this globular alpha surface layer on fatigue behavior will be discussed in the context of the ability to tune fatigue response through control of the surface layer thickness.

10:20 AM  Invited
High-strain Rate / Shock-loading Response of AM-processed Materials: George Gray1; Saryu Fensin1; David Jones1; Dan Thoma2; 1Los Alamos National Laboratory; 2University of Wisconsin-Madison
    Additive manufacturing (AM) of metals presents potential niche advantages over traditional manufacturing, with the potential for revolutionary design and production for various applications. For additive manufacturing of metallic materials, the certification and qualification paradigms continue to evolve. Accordingly, design, manufacture, and thereafter implementation and insertion of AM materials to meet dynamic loading engineering applications requires detailed quantification of the constitutive (strength and damage) properties of these evolving materials, across the spectrum of metallic AM methods, in comparison/contrast to conventionally- manufactured metals and alloys. In this talk, an overview of the structure/property behavior of dynamically / shock-loaded AM materials including 304 and 316 SS, Ti-6Al-4V, and Tantalum will be overviewed. Finally, an on-going systematic study linking the effects of AM processing parameters, including varying laser power, laser speed, hatch spacing and layer thickness on the spallation behavior of 316L SS will be discussed.

10:50 AM  Invited
Mechanical Properties of AM Deposited Metallic Components: Jan Dzugan1; Daniel Melzer1; Sylwia Rzepa1; Libor Kraus1; Mohsen Seifi2; Nima Shamsaei3; John Lewandowski4; 1COMTES FHT; 2ASTM International; 3Auburn University; 4Case Western Reserve University
    Basically there are two ways how to asses mechanical properties of AM deposited materials: deposition of separated samples for mechanical test of standard dimensions or extraction of the samples directly from the component. In many cases the component due to its complex shape and wall thickness does not allow standard samples extraction. Therefore small sized specimens are unavoidable and these can be either extracted directly from the components, of samples of similar wall thickness can be separately deposited in order to represent the real component behavior. Contribution presents mechanical properties assessment of AM deposited materials by EBM, SLM and powder blown Directed Energy Deposition systems. Local and orientation related properties with the use of miniaturized samples are presented for several single material parts as well as for multiple material ones. Results of the ASTM round robin tests related to small size tensile samples utilizations are going to be also presented.