Additive Manufacturing of Metals: Microstructure, Properties and Alloy Development: On-Demand Oral Presentations
Program Organizers: Prashanth Konda Gokuldoss, Tallinn University of Technology; Juergen Eckert, Erich Schmid Institute of Materials Science; Zhi Wang, South China University of Technology
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 1
Location: MS&T On Demand
Critical Crystallization Properties of an Industrial-Grade Zr-based Metallic Glass-Forming Alloy Used in Additive Manufacturing Measured with Fast Scanning Calorimetry: Danielle Kimmel1; Juergen Schawe1; 1Mettler Toledo
A major challenge during processing of metallic glasses is to avoid crystallization. Crystallization kinetics can be characterized using time-temperature-transformation (TTT) diagrams. With conventional techniques, such a diagram can be only measured for very slowly crystallizing alloys like Pb-based glasses. The cost of such materials limits the number of applications. The Zr-based glass-forming alloy Zr59Cu28.8Al10.4Nb1.5 is available as an industrial-grade alloy powder AMZ4, which gained great attention in laser-based additive manufacturing methods. Using Fast Differential Scanning Calorimetry (FDSC) the critical cooling and heating rates to avoid crystallization are determined to 2500 K/s and 45,000 K/s, respectively. The TTT diagram are determined upon cooling from the melt and upon heating from the gassy state. Additionally the continuous cooling transformation (CCT) diagram and the continuous heating transformation (CHT) diagram is determined.The time to crystallization of AMZ4 is very short. This may be related to the relatively high oxygen content in the powder.
Detection and Classification of Internal Defects from Surface Morphology Data of Additively Manufactured Parts: Yunwei Gui1; Kenta Aoyagi1; Huakang Bian1; Akihiko Chiba1; 1Tohoku University
The electron beam melting (EBM), one of powder bed fusion additive manufacturing technologies, is complex process, and various parameters have a huge influence on the performance of the formed part. In order to expand the use of EBM technology in the materials industry, one of the problems is the generation of internal defects (pores, un-melted powder, and so on) during process. In this research, we applied several machine learning algorithms for process optimization of the EBM process of a carbon steel, and we compared accuracy of each algorithms. We determined a quantitative criteria for classifying surface quality based on surface roughness, and we have revealed that different surface quality (uneven, even, and porous) includes different type of internal defects. Even surface samples have the highest density and hardness. In addition, six kinds of machine learning algorithms have been investigated. Among them, the SVM model has the highest accuracy.
Cryogenic Mechanical Properties of CrCoNi Medium Entropy Alloy Produced by Selective Laser Melting with Hot Isostatic Pressing: Tri Hoang Nguyen1; Minh Tien Tran1; Kyung-Hwan Jung2; Ho Won Lee3; Sun-Kwang Hwang2; Dong-Kyu Kim1; 1University of Ulsan; 2Korea Institute of Industrial Technology; 3Korea Institute of Materials Science
The present study investigated the mechanical properties and microstructure of CrCoNi medium entropy alloy (MEA) fabricated by selective laser melting (SLM) with hot isostatic pressing (HIP). The microstructure-property correlation of as-built and HIP treated CrCoNi MEA-SLM were examined by uniaxial tensile test, electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) at room (298 K) and cryogenic (77 K) temperatures. The use of HIP significantly enhances the elongation to fracture at both temperatures compared to the as-built one. At 77 K, both yield strength, ultimate tensile strength, and elongation are substantially increased. The formation of nano-twinning at 77 K examined by TEM results in the increased tensile properties compared to room temperature. Furthermore, the steady work hardening behavior, which postpones the onset of necking instability, is attributed to the interaction between dislocations and twinning. It reveals that the CrCoNi MEA-SLM with HIP possesses the excellent mechanical properties at cryogenic temperature.
Microstructural and Strength Evolution during Aging of an Additively Manufactured Al-Cu-Mn-Zr Alloy: Richard Michi1; Kevin Sisco2; Sumit Bahl1; Jonathan Poplawsky1; Lawrence Allard1; Ryan Dehoff1; Alex Plotkowski1; Amit Shyam1; 1Oak Ridge National Laboratory; 2University of Tennessee, Knoxville
Additive manufacturing enables the formation of unique microstructural features in high-temperature Al-Cu-Mn-Zr alloys. These features include a refined Al/θ-Al2Cu eutectic network, θ′-Al2Cu precipitates formed in situ during the build, and matrix supersaturations of solute elements. When heat treated, complex and simultaneous microstructural changes occur which dramatically affect strengthening mechanisms of the alloys, including coarsening of θ and θ′ precipitates and decomposition of the matrix solid solution by precipitation of nanometric L12-Al3Zr. In this talk, we review the microstructural changes occurring during aging at 300–400 °C and relate them to measured ambient- and high-temperature mechanical properties, including creep. An emphasis is placed on nanoscale microstructural and compositional analysis by APT and STEM. Insights gained are used to optimize heat treatments for alloy performance in the critical 250–400 °C temperature range. APT was conducted at the Center for Nanophase Materials Sciences (CNMS), a U.S. DOE Office of Science user facility.
Microstructure Optimization and Cracks Reduction in Cobalt Based Superalloys Processed by Directed Energy Deposition: Thibaut Froeliger1; Louise Toualbi1; Didier Locq1; Edouard Chauvet2; Arnaud Ferrandez2; Rémy Dendievel3; 1ONERA; 2Poly-Shape; 3Univ. Grenoble Alpes, CNRS, Grenoble INP, SIMaP
Additive manufacturing of cobalt-based superalloys leads to a high-textured grain microstructure. Due to thermal stresses induced by this technique, cracks can propagate along the most disoriented grain boundaries where high segregations occur.This work aims to break the columnar microstructure in order to limit the crack emergence. The investigation focuses on the modification and the optimization of the directed energy deposition parameters with no chemical composition change. Appropriate processing parameters, as well as specific scanning strategies, allow the decrease of the cracks density. Moreover, the emission of ultrasonic waves in the melt pool leads to a columnar / equiaxed microstructure transition affecting the crack density. All those results enable a better understanding of the crack initiation and a better control of the material integrity of γ’ cobalt-based superalloys.
Effect of Atomizing Gas on the Microstructure and Properties of Additively Manufactured 17-4 Precipitation Hardening Steel: Kaushalendra Singh1; George Abott1; Atieh Moridi1; 1Cornell University
The use of atomizing gas as a process parameter to tune the characteristics of manufactured parts during selective laser melting (SLM) printing has not been explored very well. In this work, we study the effect of using argon- and nitrogen-atomized powders on the microstructure and mechanical properties of 17-4 Precipitation Hardened (PH) stainless steel printed using SLM. The use of nitrogen as the atomizing gas results in the formation of powders with metastable austenitic phase and this austenitic phase is retained in the printed samples. Specimens printed with nitrogen atomized powders showed higher ductility and strength when compared to their argon atomized counterparts. Tensile tests in conjunction with electron backscattering diffraction (EBSD) have been used to study the deformation mechanism. We show that combined with post heat treatments, controlling the atomizing gas enables us to tailor the microstructure to achieve a wide range of strength-ductility values for a single composition.
Nonlinear Ultrasonic Methods for Nondestructive Evaluation of Additively Manufactured 316L Stainless Steel: Madison Sitkiewicz1; Anna Hayes1; SeHyuk Park1; Tribikram Kundu1; Krishna Muralidharan1; 1University of Arizona
Ultrasonic nondestructive evaluation methods are well established for detecting and measuring defects within engineering parts and components. Sideband peak counting (SPC) is a recently developed nonlinear ultrasonic technique used for evaluation of defects down to 10 µm. In this work, 316L stainless steel tensile test specimens were manufactured using laser powder-bed fusion (LPBF) with four levels of energy density. The ensuing porosity and its interplay with other processing defects in the different samples were evaluated using the SPC technique. In parallel, metallographic analysis in conjunction with wave propagation simulations, and mechanical testing were also carried out to complement the SPC characterization. Using machine learning methods, correlations between the SPC index of samples and the underlying porosity, defects, mechanical properties, and LPBF process parameters were obtained, thereby providing the pathway for a fully non-destructive evaluation of additively manufactured 316L stainless steel parts and components.
Functionally Graded Materials Designed by In Situ Site-specific Texture Control during Laser Powder Bed Fusion: Karl Sofinowski1; Mallory Wittwer1; Matteo Seita1; 1Nanyang Technological University
Additive manufacturing processes have a vast potential for designing functionally graded metal components. Through spatiotemporal control of processing conditions, it is now possible to produce materials with spatially variant microstructures and site-specific materials properties. Using a recently published technique, we manipulate the local solidification conditions during laser powder bed fusion of stainless steel 316L to create functionally graded materials (FGMs) with both discrete and gradient crystallographic textures. We demonstrate the potential of site-specific texture control with two applications. In the first, we leverage the anisotropic chemical properties of 316L to create a new, high-throughput method for encoding data in metals. In the second, “metamaterial” structures are designed with controlled plastic deformation. The technique demonstrated in this work can be further extended to create FGMs tailored to all material properties affected by crystallographic texture.
Development of Pure Magnesium Stochastic Foams by Additive Manufacturing: Bandar AlMangour1; Yu-Jin Hwang2; Kyu-Sik Kim3; Dariusz Grzesiak4; Kee-Ahn Lee3; 1King Fahd University of Petroleum and Minerals; 2Inha University, Incheon ; 3Inha University, Incheon; 4West Pomeranian University of Technology
The low density and high biocompatibility of Mg-based materials make them suitable for lightweight structural and biomedical applications. In this study, selective laser melting (SLM), an emerging additive manufacturing process, was used to process pure Mg foams under various laser energy densities (η). The densification behavior, microstructure evolution, and mechanical behavior were evaluated. Both the peak temperature gradients within the molten pool and the molten pool dimensions increased with increasing η, and an opposite trend was observed for the cooling rate. Low η generated low operating temperature and short liquid lifetime, resulting in poor wettability and large amount of porosity chain and balling phenomena. However, the increase in η generated melt pool instability, which resulted in extensive evaporation, cracks, and porosity, and was accompanied by an increase in the grain size due to the lower cooling rate.
Tensile Deformation Behavior of Additively Manufactured Co-Cr-Mo Lattice Structures: Bandar AlMangour1; So-Yeon Park2; Kyu-Sik Kim2; Dariusz Grzesiak3; Kee-Ahn Lee2; 1King Fahd University of Petroleum and Minerals; 2Inha University, Incheon; 3West Pomeranian University of Technology
In this work, we used selective laser melting technique to build various lattice structures made of Co-Cr alloy. The mechanical properties has been assessed by considering geometrical and microstructural aspects. Higher tensile properties (e.g., elastic modulus, energy absorption) was obtained for the fcc lattice structure. However, the tested lattice structures revealed decreased ductility during tension due to notch effects and process-related microstructure. The experimental results carried out on the lattice structures demonstrate the potential to tailor the mechanical properties by adjusting the lattice structure geometry.
Understanding the Microstructure and Magnetic Properties of the L-PBF Nd-Fe-B Permanent Magnetic Material: Julan Wu1; 1University of Nottingham
Laser powder-bed fusion (L-PBF) as an additive manufacturing technique, has demonstrated excellent capabilities in degrees of freedom in manufacturing that are otherwise unattainable. Nd-Fe-B based permanent magnetic materials having the highest magnetic energy product have attracted significant interests for the future development of more efficient and lighter motors for robots, electric vehicles, and aerospace applications. The potential of combining the functional element in Nd-Fe-B and the manufacturing capabilities of L-PBF promises new prospects for functional AM. Pure metallic Nd-Fe-B permanent magnet with high density (91%) and remanence of 0.65T has been successfully produces via L-PBF. Understanding the microstructure of the L-PBF Nd-Fe-B is essential for the development of higher density and magnetic properties. In this research, a combination of high resolution microstructural investigations with SEM, TEM and metallurgy studies with EDS, XRD and EBSD will bring new insight into the understanding of L-PBF Nd-Fe-B material.
Effects of Controlled Porosity on Additively Manufactured Stainless Steel 316L Subject to Dynamic Loading: Katie Koube1; Kevin Lamb2; Taylor Sloop1; Sudarsanam Babu2; Naresh Thadhani1; Josh Kacher1; 1Georgia Institute of Technology; 2University of Tennessee Knoxville
This presentation describes the influence of porosity in the dynamic (spall) failure of powder bed fusion (PBF) stainless steel 316L (SS316L) under impact testing. Samples were fabricated with porosity levels of 1%, 3% or 5% volume and pore sizes of 200, 350 or 500 microns in diameter. PBF manufactured cylinders were impacted using an 80-mm gas gun at pressures of approximately 4.2 GPa to generate spall failure. Spall strength and failure responses of PBF SS316L vary based on the frequency and size of pores. Photon Doppler velocimetry (PDV) was used to capture free surface velocity profiles during plate-impact experiments, and post mortem electron backscatter diffraction (EBSD) in combination with SEM and image analysis was used to explore local defect structures and determine the role of porosity on spall initiation. This talk will discuss the effects of heterogeneous microstructural defects and pore distribution on the initiation of dynamic tensile (spall) failure.
An Investigation of Elastic Properties of Coal-derived Graphene-reinforced Aluminum Nanocomposites Using Friction Stir Welding and Molecular Dynamics Simulations: Saurav Kar1; Roop Mahajan1; 1Virginia Tech
In this paper, we report the findings of our experimental and numerical investigations of the elastic and shear properties of coal-derived graphene flakes-reinforced aluminum nanocomposites. Multilayer graphene flakes were exfoliated using our in-house developed single acid one-pot process. Number of stacking layers, shape and morphology were varied by changing acid concentration and temperature during synthesis of flakes from different ranks of coal. Graphene flakes-aluminum nanocomposites were then fabricated using friction stir welding—a solid-state additive manufacturing process—, which also selectively aligns flakes along the stirring plane. Elastic and shear moduli were then experimentally tested using an Instron universal testing machine. Numerical models were analyzed using molecular dynamics simulations. The experimental and simulation results illustrate that elastic properties of graphene flakes-reinforced aluminum nanocomposites are correlated to flake shape, size, and the number of stacking layers. Coal-derived graphene flakes are shown to be an effective reinforcement material with tunable material characteristics.
Oxide Layer Delamination during Single Cu Microparticle Impacts at High-velocity: Ahmed Alade Tiamiyu1; Yuchen Sun1; Keith Nelson1; Christopher Schuh1; 1Massachusetts Institute of Technology
Cold-spray additive manufacturing is a solid-state layer-by-layer deposition of microparticles at high velocity to form coatings on a substrate. A significant concern in this process is the presence of native surface oxide layers on metallic particles. A well-accepted requirement for permanent particle adhesion is that surface oxides must be removed to permit clean metal-metal contact. Using a laser-induced particle impact tester, we conduct direct optical observations of single Cu microparticle impacts on a polished Cu substrate and characterize impact sites to seek evidence for oxide layer fracture and disruption at experimentally controlled impact velocities. We observe that the surface oxide layer of the particle delaminates upon impact at the same range of velocities where substrate jetting occurs. We further show that such delamination process involves energy dissipation during impact that consumes about 30% of the extra energy expended beyond the plasticity of the impact.
Influence of Bead’s Geometry on the Residual Stresses, Structure and Mechanical Behavior in Wire Arc Additive Manufacturing: Ahmed Elsokaty1; Sameha Sadek1; Maha Elsaied1; Omar Gadalla1; Hadeer Achraf1; Hanadi Salem1; 1American University in Cairo
Wire Arc Additive Manufacturing high deposition rates have attracted the interest of industry for the demonstrated economical production of medium-to-large scale metallic components. Structural integrity and mechanical properties of the built parts are fully dependent on the selection of the optimum deposition parameters and the tool path strategy. In this study, additive robotic controlled system was employed for building orthogonal multi-layered prismatic steel blocks with different beads’ width and beads’ overlapping distances. The influence of the beads’ geometry on the structural evolution and mechanical properties along the building direction of the deposited blocks were characterized. Prediction of the generated stresses and strains along the building direction were simulated using Direct Energy Deposition module of Simufact welding. For the same overlapping distance, the wider the bead the lower the residual stresses, while for the same bead width the higher the overlapping distance the higher the residual stresses along the building direction.
The Significant Impact of Grain Refiner on Additively Manufactured TiAl Intermetallic Alloy: Danni Huang1; Mingxing Zhang1; Ming Yan2; 1The University of Queensland; 2Southern University of Science and Technology
TiAl intermetallic alloy is emerging as a significant engineering material in high temperature applications due to its high strength and good corrosion, creep and oxidation resistance at elevated temperature. Additive manufacturing (AM) has been considered as a powerful tool to fabricate TiAl intermetallic alloy. However, intermetallic TiAl alloy due to its intrinsic brittleness could not accommodate the high thermal stress generated by fast cooling rate and high thermal gradient during AM process, resulting in distortion and cracking. In our study, grain refinement technology was integrated to additive manufacturing of a Ti-44Al-4Nb-1Mo-1Cr (in at.%) intermetallic alloy to improve its AM processability. Crack-free and fine-grained samples could be successfully fabricated through grain refinement. The compressive yield strength, compressive strength and strain are simultaneously increased by 29%, 12.4% and 61.9% respectively. The mechanical performance of this modified alloy is comparable or even better than those produced by conventional technologies.
Physical and Mechanical Properties of Aluminium Bronze - Stainless Steel Binary Alloy after Laser Metal Deposition: Konstantin Makarenko1; Oleg Dubinin1; Igor Shishkovsky1; 1Skolkovo Institute of Science and Technology
This work presents the results of theoretical and experimental analysis of a laser deposited two-component material created from powder composition of aluminium bronze and SS 316L at the ratio 3:1. Microstructure parameters and mechanical properties (yield and ultimate stresses, Young's modulus, Poisson's ratio, microhardness) and thermal expansion coefficients (TECs) were measured for the binary alloy and compared with pure aluminium bronze and stainless steel. The linear TEC amounted 1.362 1/K what is slightly lower than TECs of initial materials. Ultimate tensile stress amounted 713.7 MPa. A main field of practical application of such dual materials is operating under external forces in extreme temperature conditions and aggressive alkaline and salt atmospheres. Such alloys also can be used as a general or intermediate components for additive manufactured functionally graded Cu-Fe system materials applied in aerospace and nuclear industries, processing equipment and electronic components producing.
Effects of Laser Polishing Parameters on Surface Roughness of Additively Manufactured Stainless Steel 316L Parts: Daniil Panov1; Oleg Oreshkin2; Igor Shishkovsky1; 1Skolkovo Institute of Science and Technology; 2National Research Nuclear University MEPhI
As-built surface condition of the additively manufactured parts does not satisfy many industries requirements. Selective Laser Melting provides one of the lowest final roughness compare to other metal additive manufacturing methods. However, the surface roughness Ra usually varies from 5 to 30 μm and depends on processing parameters and conditions. The research considers the application of laser polishing to surface finishing of additively manufactured parts. AISI 316L was chosen as the primary material for the research. The polishing was provided by Continuous Wave laser radiation with power up to 200 W. The impact of processing parameters on the after-processing roughness was shown. The influence of the laser polishing on the material properties was shown. The quantitative analysis of laser polishing for reduction of waviness and high-frequency roughness was provided. For the best set of processing parameters, the roughness of the as-built part was reduced from Ra 11 to 0.9 μm.