Additive Manufacturing: Length-Scale Phenomena in Mechanical Response: Deformation Mechanisms and Mechanical Properties
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Meysam Haghshenas, University of Toledo; Andrew Birnbaum, Us Naval Research Laboratory; Robert Lancaster, Swansea University; Xinghang Zhang, Purdue University; Aeriel Leonard

Tuesday 2:30 PM
March 21, 2023
Room: 23B
Location: SDCC

Session Chair: Somayeh Pasebani, Oregon State University; Xinghang Zhang, Purdue University


2:30 PM  Invited
Understanding the Strength and Ductility of Additively Manufactured Metals across Various Length Scales: Yinmin (Morris) Wang1; 1University of California - Los Angeles
    The unique microstructure and multiple length scales observed in metals and alloys prepared by additive manufacturing impose unprecedented challenges to investigate and understand their mechanical properties. New experimental tools and modeling effort are often required to fully interpret their mechanical performance. Strength and ductility are two fundamental and perhaps most important properties of the additively manufactured metals. This talk will focus on our recent effort in creating high strength and high ductility metals/alloys via additive manufacturing techniques, including laser powder-bed-fusion and wire arc additive manufacturing. Several prominent examples will be given and influencing factors will be discussed in each case. Relevant modeling results will be presented whenever possible in an attempt to deepen our understanding of length scale and residual stress effects on mechanical properties.

2:50 PM  
Multi-scale Tensile Deformation of Wire Arc Additive Manufactured Titanium from Microscopic Beads to Macroscopic Component: Tanaji Paul1; Blanca Palacios1; Denny John1; Kazue Orikasa1; Tyler Dolmetsch1; Sohail Mohammed1; Gonzalo Seisdedos1; Sean Langan1; Alex Michelson1; Cheng Zhang1; Arvind Agarwal1; 1Florida International University
    Wire arc additive manufacturing (WAAM) is a promising technique for manufacturing commercially pure titanium (cp-Ti) components for marine applications such as engine and propeller blades. Absence of understanding the hierarchical mechanical response of WAAM-ed cp-Ti from single solidified beads through deposited layers to bulk component restricts process tailoring for manufacturing mechanically durable parts. This paper establishes the multi-length scale tensile behavior of WAAM-ed cp-Ti components using an integration of microscopic indentation plastometry, mesoscopic in-situ image analysis, and bulk uniaxial tensile tests. At microscopic scale, monolithic grain structures result in uniform yield strength of 330 MPa, 94% of cast cp-Ti while at mesoscopic scale interlayer phenomena such as grain rotation sustains the strain. Cumulatively, these phenomena enable the highest ductility of 29% in the additive build direction at the bulk macroscopic scale. The comprehensive understanding of the multi-scale tensile plasticity harbors potential for advancement in the large scale WAAM of cp-Ti

3:10 PM  
Characterizing Inhomogeneous Deformation Across Melt Pool Boundaries in Additively Manufactured Parts: John Fite1; Suhas Prameela1; John Slotwinski2; Tim Weihs1; 1Johns Hopkins University; 2JHU Applied Physics Lab
    The Powder Bed Fusion (PBF) additive manufacturing (AM) process produces metal parts with a wide variety of complex and intricate components. Although AM parts are often considered to be uniform bulk materials, our results from AlSi10Mg show that AM parts containing melt pool boundaries have unique local mechanical properties. Specifically, we use in situ SEM tensile testing and digital image correlation under load to show that deformation is higher within the melt pool boundaries compared with other regions in AlSi10Mg samples. We correlate unique melt pool boundary microstructures (like cell size and the heat affected zone) with tradeoffs in local mechanical properties and deformation characteristics, and we report ductility and tensile strengths for AlSi10Mg samples. The measured differences in local deformation suggest that predictions of properties of AM parts should account for the presence of melt pool boundaries.

3:30 PM  
Mechanical Response of Tailored 304L Stainless Steels, Processed with L-PBF, under Different Stress States: Christos Sofras1; Jan Capek1; Markus Strobl1; Efthymios Polatidis1; 1Paul Scherrer Institute
    Apart from the profound advantage of producing complex geometries, laser-powder bed fusion (L-PBF) provides the possibility of manipulating microstructures and crystallographic textures. By combining the texture-manipulation capabilities of L-PBF with the strong orientation-dependence of the transformation induced plasticity (TRIP) and the twinning induced plasticity (TWIP) effects, it is possible to realize L-PBFed alloys with equal or even superior mechanical properties compared to their wrought counterparts. In this contribution, the mechanical behavior of a 304L steel processed with L-PBF and with locally tailored crystallographic textures will be shown. Uniaxial tension, compression and equibiaxial tests, paired with in-situ neutron diffraction and EBSD analysis, enable monitoring the microstructural evolution during deformation. Additionally, quasi-static EBSD measurements are performed on multi-textured specimens subjected to V-bending tests. The present investigation highlights how tailored microstructures, produced by L-PBF, lead to different mechanical responses and paves the way for tailored materials with enchanced strength and energy dissipation applications.

3:50 PM Break

4:10 PM  
Deformation Behavior of Aluminum Alloys Deposited by Laser Hot-wire Manufacturing: Gerry Knapp1; Maxim Gussev1; Amit Shyam1; Thomas Feldhausen1; Alex Plotkowski1; 1Oak Ridge National Laboratory
    Laser hot-wire additive manufacturing (AM) heats a wire via Joule heating before fully melting it with a laser beam to form a part. Here, we apply this AM technique to aluminum alloys, which are sensitive to heat accumulation during multi-layer fabrication due to their low melting temperature. To understand the deposited alloy's deformation, tensile testing was done with digital image correlation. Characterization of the microstructure in the deformed specimens by scanning electron microscopy, optical microscopy, and electron backscatter diffraction was correlated with the transient local strain data from the tensile tests. The deformation was shown to be localized in the melt pool boundary regions, which correlated with variation in the microstructure morphology of the melt pool boundary regions. These results will be discussed in terms of the microstructure-property relationships of as-built aluminum alloys. This work was supported by the U.S. Department of Energy Vehicle Technology Office Lightweight Metals Core Program.

4:30 PM  
Microstructures and Deformation Mechanisms in Additively Manufactured 316L Stainless Steels: Thomas Voisin1; Marissa Linne1; Jean-Baptiste Forien1; Nicolas Bertin1; Tatu Pinomaa2; Anssi Laukkanen2; Kirubel Teferra3; Margaret Wu1; Sylvie Aubry1; Y. Morris Wang4; Nathan Barton1; 1Lawrence Livermore National Laboratory; 2VTT Technical Research Center of Finland; 3US Naval Research Laboratory; 4University of California Los Angeles
     Rapid thermomechanical cycles during laser powder-bed-fusion (L-PBF) additive manufacturing (AM) gives as-fabricated metals none-equilibrium microstructures, most often resulting in improved properties. In L-PBF 316L stainless steels (316LSS), this means breaking off the strength/ductility tradeoff. So-called cellular structures have explained the significant increase in strength. However, these structures are complex, with high density dislocation cells containing precipitates and trapped solutes. We will present our recent investigations of the plasticity of L-PBF 316LSS, first introducing the multi-scale microstructural features present in the as-fabricated and annealed materials. The second part will focus on how we test, characterize, and simulate the plastic deformation of L-PBF 316LSS materials, with and without post-process heat treatment. We use electron microscopy (SEM and TEM), in-situ high energy X-ray diffraction (HEXRD), cellular automata, crystal plasticity simulations, and virtual HEXRD. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

4:50 PM  
Utilizing Profilometry-based Indentation Plastometry, Nanomechanical Property Mapping and Flat-punch Nanoindentation to Unveil Dynamic Recrystallization-to-Plasticity Relations in Cold Spray Additive Manufacturing: Bryer Sousa1; Danielle Cote1; 1Worcester Polytechnic Institute
    The formation of heterogeneous strain gradients throughout consolidated metallurgical cold spray microstructures stems from high-strain rate impact-induced severe plastic deformation mechanisms. Consequently, the particle-particle bonding underpinning solid-state cold spray processing is accompanied by interfacial dynamic recrystallization under a wide range of applied impact stresses, point-of-impact strain rates, and particle impact velocity regimes. However, the degree of dynamic recrystallization achieved along said interfacial zones have yet to be entirely or mechanistically connected to the plasticity characteristics of consolidations as a function of processing parameters. This work considers gas-atomized metallic feedstock in conjunction with variable processing parameter sets (carrier gas pressure and temperature modulation) to obtain metallurgical consolidations with differing degrees of interfacial dynamically recrystallized zones. Using profilometry-based indentation plastometry, flat-punch nanoindentation, and nanomechanical property mapping, linkages between the degree of recrystallization and plasticity will be unveiled through multi-scale indentation mechanics and guide enhanced processing-structure-properties-performance relations for cold spray additive manufacturing.