Additive Manufacturing: Length-Scale Phenomena in Mechanical Response: Microstructural Features II
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 8:00 AM
March 21, 2023
Room: 23B
Location: SDCC

Session Chair: Keivan Davami, The University of Alabama; Vikas Tomar, Purdue University


8:00 AM  
Toward Developing Processing-Microstructure-Property Prediction to Enable Digital Twins of Additive Manufacturing Process: Mohsen Taheri Andani1; Veera Sundararaghavan1; Amit Misra1; 1University of Michigan
    Metal additive manufacturing (AM) promises to benefit significantly from using digital twins (DTs). This is due to the chaotic nature of the AM process, which results in poor reproducibility. Nonetheless, a DT in a supervisory capacity may inject assurance into the process by actively enforcing the process's boundaries with real-time control instructions. Developing physics- and data-driven methodologies for investigating processing-structure-property interactions is a crucial step in developing the DT for AM components. This paper presents an unsupervised machine learning technique for predicting the relationship between manufacturing process parameters, such as laser scan strategy and building orientation, microstructure features, such as crystallographic texture and grain boundary type, and the mechanical performance of metal AM components. The approach uses sensor information from the printer to improve upon thermal cycling predictions, leading to control of microstructure. Applications of the method to controlling texture, grain boundary character and phases are presented.

8:20 AM  
Kinetically-Driven Microstructure and Mechanical Properties of 3D Micro-architected Metal Alloys formed via Hydrogel Infusion Additive Manufacturing (HIAM): Thomas Tran1; Rebecca Gallivan1; Julia Greer1; 1California Institute of Technology
    Hydrogel infusion-based additive manufacturing (HIAM) is unique in its absence of melt solidification. By nucleating parent oxides and subsequently reducing them, HIAM provides a kinetically-driven pathway for forming boundaries in polycrystalline metal microarchitectures. Using EBSD and TEM analysis, we characterize the microstructural features within HIAM-produced Cu, Ni, and Cu-Ni alloys. These metals and alloys exhibit anomalous nanoindentation hardnesses, exceeding predictions by the Hall-Petch relation by over 30%, which we postulate as due to the network of high-angle, annealing twin, and higher-order coincident site lattice boundaries. We explore these formed boundaries by conducting site-specific compression experiments on nano- and micropillars carved from individual grains -- as well as spanning specific boundaries --, isolating each contribution to plasticity in HIAM-produced metals. We present a phenomenological framework accounting for the contribution of special boundaries to global mechanical properties, which helps inform HIAM as a novel means for architecting alloys with non-equilibrium microstructures.

8:40 AM  
A Novel Continuous-wave Laser and SEM Coupling: Application to Engineer an Additively Manufactured Microstructure: Juan Guillermo Santos Macias1; Alexandre Tanguy1; Manas Upadhyay1; 1Ecole Polytechnique
     We have developed a novel and unique coupling between a continuous-wave laser and an environmental-SEM. This novel device can help identify in-process/post-process laser treatments that can be performed inside an AM chamber in order to improve the surface quality and mechanical response of parts. Ultimately, it can even shed light into the microstructural changes induced due to solid state thermal cycling during AM.In this talk this unique device is first introduced. Then, the results of a series of laser scanning tests are presented, followed by the results of tensile and fatigue testing of a laser-scanned AM 316L steel microstructure. Through EBSD and other microscopy techniques, texture, grain morphology, dislocation density and strain changes are analysed. The results show that the laser scanning has improved the mechanical response of the as built material.

9:00 AM  
A Multiscale Study of the Interconnection between Unit Cell Design, Processing Conditions, Microstructure, and Mechanical Properties of Additively Manufactured Titanium Metamaterials: Massimiliano Casata1; Conrado Garrido1; Toby Wilkinson1; Enrique Alabort2; Daniel Barba1; 1Universidad Politécnica de Madrid; 2Alloyed
    Metallic architected metamaterials are a class of materials that combine properties of bulk alloys with tailored latticed geometries. The variety of characteristic sizes and orientations of the elementals forming these kinds of materials is vast. When produced by additive manufacturing (AM), this is an acute problematic as the mechanical properties of AM alloys depend strongly on the size and orientation of the printed geometry due to processing and microstructural variations. In this work, this problem is tackled by a systematic multiscale approach of the metamaterial design – microstructure – mechanical properties’ interconnection. Titanium alloys processed by selective laser melting are used as base material. Rationalization by means of combined experimentation and simulations of low-scale elemental beam behavior ranging from 400 microns to mms including orientation and size effects provide a physical explanation for the macro-scale behavior of architected metamaterials. Microstructure, roughness, and defects are connected with the metamaterial design.

9:20 AM  
Effect of Grain Microstructure on the Deformation Behaviour of Inconel 718 Fabricated by Laser Powder-bed Fusion: An In-situ Study: Jalal Al-Lami1; Thibaut Dessolier1; Talha Pirzada2; Minh-Son Pham1; 1Imperial College London; 2University of Oxford
    Additive manufacturing is widely regarded as a disruptive technology because of its unique capacity to create builds of structurally complex geometries on a macroscopic-scale and tailored metallurgical microstructures on a fine-scale. This talk examines the effects of altered microstructures of Inconel 718 created by laser powder-bed fusion using varied scanning strategies on the deformation behaviour. The examination was performed using in-situ tensile testing coupled with electron backscatter diffraction, scanning electron microscopy and optical microscopy. The deformation behaviour was correlated with the grain size, dislocation density and crystallographic orientations. Special attention was paid to study the heterogeneous slip activities. It was found that the heterogeneity was enhanced in regions of clustered fine, but “soft” <001> grains and in the vicinity of the boundaries between soft <001> and hard <111> grains with respect to the loading direction. The evolution of the crystallographic texture with increasing strain intervals was quantified and discussed.

9:40 AM Break

10:00 AM  
Local Control of Strain, Microstructure, and Properties in Ti-5553 Lattice Materials: Caleb Andrews1; Jenny Wang2; Maria Strantza2; Manyalibo Matthews2; Mitra Taheri1; 1Johns Hopkins University; 2Lawrence Livermore National Laboratory
    The manufacture of architected materials via laser powder bed fusion additive manufacturing (L-PBF AM) enables the tailoring of properties through variation of geometry and topology. Simultaneously, controlling the laser processing parameters within L-PBF allows for the tuning of the local solidification environment, which can be used to tailor the microstructure of a material. In combining these approaches and varying the laser parameters within the node of an architected lattice cell, locally tuned microstructures, residual strains, and mechanical properties can be induced. Using an approach of high-resolution electron backscattering diffraction, micromechanical hardness measurements, and in-situ melt pool monitoring, a link between processing conditions, microstructure, and properties is established from the microscale to the mesoscale of a lattice cell. By enabling tuneability of microstructures and microstrains within the ‘0th-order’ scale of a single lattice strut or node, additional degrees of property enhancement and tailorability can be achieved with architected materials.

10:20 AM  
Impact of Nanoscale Intermetallic Dispersions in Al-Ce Alloys for Selective Laser Melting: Hunter Henderson1; Alfred Amon1; Alexander Wilson-Heid1; Zachary Sims1; Orlando Rios2; Ryan Ott3; Scott McCall1; 1Lawrence Livermore National Laboratory; 2University of Tennessee-Knoxville; 3Ames Laboratory
    Aluminum-cerium is a promising system for alloys adapted to Selective Laser Melting (SLM). The eutectic nature of the phase diagram results in good printability, while the low mobility of Ce in liquid Al results in a nanoscale dispersion of intermetallic particles in alloys produced by SLM. Further, the near-zero solubility of Ce in Al makes these intermetallics highly resistant to thermal coarsening during SLM and subsequently in service. The hard intermetallics can change the material’s elastic response through changes in load sharing characteristics, both as a function of contiguity and volume fraction. Here, we discuss recent investigations of Al-Ce alloys for SLM that leverage rapid solidification to produce materials with unusual strength and elastic response, as characterized by in situ mechanical testing, microhardness testing, and other methods. The possibilities and implications of hypereutectic Al-Ce alloys with metastable solidification pathways will also be discussed.

10:40 AM  
Enhanced Tensile Ductility of an Additively Manufactured AlSi10Mg Alloy by Reducing the Density of Melt Pool Boundaries: Haoxiu Chen1; Yu Zou1; 1University of Toronto
    AlSi10Mg components produced by laser powder bed fusion (LPBF) typically exhibit higher strength but lower ductility than those made by conventional mature processing technologies. The effects of melt pool boundaries on the ductility and fracture behavior of the LPBF-produced AlSi10Mg have not been systematically studied. The focus of this work is to investigate the local strain evolution, microvoid growth, and crack formation in the melt pool boundary regions using in situ tensile testing and synchrotron-based X-ray microtomography. Results indicate that decreasing area fractions of melt pool boundaries from 5.48% to 4.48% leads to an increase of tensile ductility from 7.2% to 9.8% in the LPBF AlSi10Mg samples. By influencing the density of melt pool boundaries in the LPBF process, while maintaining part density, we offer a new opportunity to fabricate AlSi10Mg products with an excellent combination of high strength and ductility.