Additive Manufacturing Fatigue and Fracture IV: Toward Confident Use in Critical Applications: Processing-Structure-Property-Performance I
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; Steve Daniewicz, University of Alabama; Nima Shamsaei, Auburn University; John Lewandowski, Case Western Reserve University; Mohsen Seifi, ASTM International/Case Western Reserve University
Monday 8:00 AM
February 24, 2020
Room: 7B
Location: San Diego Convention Ctr
Session Chair: Mohsen Seifi, ASTM International
8:00 AM Invited
Performance of Recycled Metal Machine Chips and Strips Through Solid Phase Additive Manufacturing: Paul Allison1; J. Brian Jordon1; Luke Brewer1; Kevin Doherty2; 1University of Alabama; 2US Army Research Lab
Additive Friction Stir-Deposition (AFS-D) provides a rapid, flexible, and robust metal recycling option that may be applied to manufacture large-scale multi-material components and/or repair damaged structures (i.e. vehicles, armor systems, etc.) while in-theatre thus reducing the associated lead time. This presentation summarizes an experimental and computational investigation on the solid-phase processing of two waste streams: (1) manufacturing chips and (2) field-damaged stacked strips via AFS-D. X-ray Computed Tomography (CT) analyses shows fully-dense depositions while isotropic mechanical behavior is observed in large test articles. Furthermore, the in-depth experimental datasets characterizing microstructure, residual stresses, and mechanical performance are being used to develop multiscale computational models for predicting material performance. The fundamental understanding compiled on this study could serve as the groundwork to transition AFS-D to a mobile and economical manufacturing platform.
8:30 AM
Effect of Build Orientation and Post Machining on AM 316L Part Failure: Michael Heiden1; Dan Tung1; David Saiz1; Bradley Jared1; 1Sandia National Laboratories
In the quest for developing more consistent and reliable additively manufactured (AM) parts, it’s known that surface roughness and porosity negatively affect mechanical performance. However, predicting how an AM part will perform and where it will fracture is still an unknown. In this study, electrical discharge machining (wire-EDM) was used to cut tensile samples out of blocks of 316L stainless steel, printed using laser-powder bed fusion (L-PBF). With the reduction of roughness and sites for surface crack initiation, failure mechanisms could be identified in various orientations. UTS, YS, and ductility all increased, except for two orientations. Positioning in the build chamber and angle of parts were found to contribute significantly to changes in microstructure, fracture site, crystallographic texture, hardness, and porosity. How slight changes to build orientation and post-processing can affect resulting mechanical performance will be discussed.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
8:50 AM
Additive Manufacturing of Bulk Refractory High Entropy Alloys with Tailored Mechanical Properties: Jonathan Pegues1; Michael Melia1; Shaun Whetten1; Nicolas Argibay1; 1Sandia National Laboratories
The design space offered by additive manufacturing has introduced new methods to rapidly explore the composition-properties space of multimaterial systems. Techniques, such as powder based directed energy deposition, allow for spatial compositional grading of multiple metals, such that a single specimen can consist of a wide composition range with site-specific properties. Combining this fabrication technique with high throughput characterization techniques allows for rapidly elucidating the alloy process-structure-property relationships. In this study, refractory metals were incrementally introduced to an equiatomic CoCrFeMnNi high entropy alloy to investigate the microstructure and mechanical properties evolution as a function of composition. Results show that exceptionally high hardness can be achieved for bulk material in the medium to high configurational entropy range. Hardness results are discussed in the context of the alloy configurational entropy and microstructure.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
9:10 AM
Linking Porosity Characteristics to the Mechanical Properties of Additive Manufactured AlSi10Mg and 316 Stainless Steel: Christopher Laursen1; Jay Carroll1; Philip Noell1; David Moore2; 1Sandia National Laboratories, Materials Mechanics and Tribology; 2Sandia National Laboratories, Nondestructive Evaluation and Experimental Mechanics
Considerable work has gone into limiting porosity in additively manufactured (AM) metallic components, yet it is likely it will remain an ever-present feature moving forward. Realizing this, a greater understanding of what role pore characteristics, such as shape, size, relative proximity, and overall density have on the mechanical properties of a material is necessary. The presented work considers two AM materials ranging the ductility spectrum, including as-built AlSi10Mg and 316L stainless steel. Non-destructive techniques such as computed-tomography and Archimedes’ density were used. These results were compared to mechanical results from tensile tests including ductility, tensile strength, and failure location to draw correlations between pore characteristics and bulk mechanical properties. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
9:30 AM Break
9:50 AM Invited
Mechanical Behavior of Induced Lack of Fusion Flaws in AlSi10Mg: Brett Conner1; John Lewandowski2; Austin Ngo2; Varthula De Silva Jayasekera1; Griffin Jones3; Kenneth Meinert3; 1Youngstown State University; 2Case Western Reserve University; 3Pennsylvania State University Applied Research Lab
It is desirable to use laser powder bed fusion to fabricate replacement parts that are flight critical. In order to gain confidence in the additive process during qualification and certification, it is important to understand the effects of rogue flaws on the properties and service life of a part fabricated by laser powder bed fusion. The performance of nominal (defect-free) material must be compared to material with readily detectable flaws as well as material with difficult to detect flaws. Here, several sizes of lack of fusion defects are created in AlSi10Mg parts by systematically varying process parameters to create insufficient melt pool overlap. Parts are fabricated with selective placement of flaws of various sizes. Nondestructive evaluation is conducted using computed tomography, radiographic testing, and phase compensated resonance testing. Next, tensile strength, constant amplitude fatigue strength, fracture toughness, and fatigue crack growth resistance are measured and reported.
10:20 AM
Predicting the Integrity of Additively Manufactured Nickel Alloys: Quantifying the Evolution of Texture and Elastic Constants Using Resonant Ultrasound Spectroscopy: Jeffrey Rossin1; Marie-Agathe Charpagne1; Brent Goodlet1; Chris Torbet1; Michael Groeber2; Bill Musinski2; Jonathan Miller2; Stephen Smith3; Samantha Daly1; Tresa Pollock1; 1University of California, Santa Barbara; 2Air Force Research Laboratory; 3NASA Langley Research Center
Additive manufacturing (AM) has enabled the creation of components with complex geometries, unique processing advantages, and simplified designs. Despite the advantages of AM, difficulties in qualifying AM components for critical applications has limited its widespread usage. Variables such as beam settings, part geometry, and material specific parameters cause variation in microstructure between additive parts and builds. Resonant Ultrasound Spectroscopy (RUS) is being investigated as a non-destructive evaluation (NDE) technique that can characterize and qualify additively manufactured nickel alloy components. RUS has been used to study microstructure and texture for a nickel-base alloy printed by laser powder bed. Using a single AM sample, RUS has enabled quantification of the elastic constants as they evolve during stress relief and recrystallization. The effect of grain nucleation and intergranular misorientation will be discussed. These findings have been validated using finite element simulations. Model and experimental results present further defect detection capabilities via RUS.
10:40 AM
Flaw Identification in Additively Manufactured Components: Capabilities and Limitations: Griffin Jones1; Rachel Reed2; Jayme Keist1; Zackary Snow1; Veeraraghavan Sundar2; 1Penn State; 2UES, Inc.
In additive manufacturing (AM), internal flaws that form during processing can have a detrimental impact on the resulting fatigue behavior of the component. Nondestructive X-ray computed tomography (CT) has been routinely used to inspect AM components. This technique, however, is limited by what is resolvable as well as the automated procedures available to analyze the data. In this study, we compared X-ray CT scans and automated defect recognition (ADR) analysis of the data to results obtained from an automated mechanical-polishing based serial sectioning system. Although the internal porosity, microcracks and surface roughness were easily observed by serial sectioning with bright field optical microscopy, the same level information could not be obtained from the X-ray CT data or from the automated defect recognition (ADR) algorithms. The results point to the limitations of X-ray CT as well as highlighting the need for further ADR development for flaw identification in AM components.