Additive Manufacturing: Materials Design and Alloy Development IV: Rapid Development: On-Demand Oral Presentations
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Behrang Poorganji, Morf3d; Hunter Martin, HRL Laboratories LLC; James Saal, Citrine Informatics; Orlando Rios, University of Tennessee; Atieh Moridi, Cornell University; Jiadong Gong, Questek Innovations LLC

Monday 8:00 AM
March 14, 2022
Room: Additive Technologies
Location: On-Demand Room


Relationship between the Solidification Behavior and Porosity in Gas-atomized Powders and Electron Beam Melted Co-Cr-Mo Alloys: Kenta Yamanaka1; Shoya Aota1; Jérôme Adrien2; Eric Maire2; Damien Fabrègue2; Akihiko Chiba1; 1Tohoku University; 2INSA Lyon
    Eliminating the powder-originated porosity in additive manufacturing is challenging in designing and fabricating highly durable components. In this study, we examined the formation of pores during gas atomization and subsequent electron beam melting (EBM) processes of the Co-27Cr-6Mo alloys with a wide range of carbon contents (0.04-2.5 mass%). X-ray CT successfully captured spherical gas pores in both raw powder and as-built specimens. The porosity and pore size in powders increased with increasing the carbon content. In contrast, part of pores was eliminated during the EBM process and the low-carbon alloys showed negligible porosity. Notably, a dramatic decrease in the porosity during the EBM process was observed in the as-built specimen with 2.5 mass% carbon. Such a variation could be correlated with the change in the solidification microstructure and demonstrated that a smooth solid-liquid interfaces in the cellular or eutectic solidification effectively eliminates gas bubbles in the melt pool.

Towards Scaling Law-based Process Screening in Laser Powder Bed Fusion by Melt Pool Control: Theresa Hanemann1; Christoph Seyfert2; Astrid Rota2; Martin Heilmaier1; 1Karlsruhe Institute of Technology; 2EOS GmbH Electro Optical Systems
    A major drawback to the industrialization of laser powder bed fusion is the comparably small selection of commercially available metals and alloys. With the development of LPBF-adapted compositions processing and according property windows have to be defined for those new alloys. Using scaling laws which relate process parameters to thermophysical material properties enable a fast selection of suitable processing parameters. In this study a modified dimensionless enthalpy equation was correlated with melt pool dimensions of single line scans for four different alloys (In718, 316L, Ti6Al4V, M300). From the boundary conditions on melt pool depth to form a stable and defect free melt pool a common process window could be defined for these alloys. The variation of melt pool dimensions, e.g. surface area to melt volume, within this process window influences the resulting microstructure and thus can be used subsequently to deduce final part properties.

Effect of Laser Parameters on The Microstructure and Formation of TiC-Fe Cermets Fabricated through Selective Laser Melting: Himanshu Maurya1; Prashanth Gokuldoss1; Lauri Kollo1; Marek Tarraste1; Kristjan Juhani1; Fjodor Sergejev1; 1Tallinn University of Technology
    The influence of pulse shaping and regular pulse on the microstructure and formation of TiC-Fe based cermets are investigated. This research focuses primarily on the process parameters required to produce defect-free (pores and cracks) components and their mechanical properties such as hardness and fracture toughness. To acquire an optimal process parameter, samples were manufactured using pulse shaping technology and a regular laser pulse wave with varying laser peak power and exposure time. No cracks are observed on the surface of the sample processed through pulse shaping indicated that the pulse shaping technique is beneficial for crack elimination and optimal for processing TiC based cermets. Post-processing treatment such as HIP was adapted to study the effect on the microstructure and mechanical properties on the pulse-shaped SLM processed samples. Pulse-shaped laser-produced samples had the highest hardness and fracture toughness (1008 MPa and 16.7 MPaM1/2, respectively) compared to their counterpart without pulsing.

Functionally Graded Alloys from 316 Stainless Steel to Inconel 718 by Powder-based Laser Direct Energy Deposition: Kun Li1; Jianbin Zhan1; Qian Tang1; David Zhang2; Wei Xiong3; Huajun Cao1; 1Chongqing University; 2Chongqing University; University of Exeter; 3University of Pittsburgh
    Additive manufacturing (AM) is an efficient method to fabricate complex geometry functionally graded materials (FGMs) with gradually variable composition and structures as a function of position, allowing for the local tailoring of properties instead of the costly need for extraneous welds and joints. In this work, a laser-based directed energy deposition (DED) process was carried out to develop a series of compositionally graded joints from 316 stainless steel to Inconel 718 alloy through computational analysis and experimental characterization. Compared to the traditional joint, AM graded materials have more gradient composition and microstructure, with a complex evolution of phases like MX and Nix(Al,Ti,Nb) during printing and post homogenization heat treatment. The computational-experimental approach is a promising method to design good properties of dissimilar metal joints. The gradient zone that can be flexibly tuned by AM process provides a high throughput design through local tailoring of properties to develop new functional materials.

Cancelled
Development of a CoNi-based Superalloy with a Focus on As-printed Microstructure: Kira Pusch1; Sean Murray1; Evan Raeker1; Ning Zhou2; Stephane Forsik2; Tresa Pollock1; 1University of California, Santa Barbara; 2Carpenter Technology
    Additive manufacturing (AM) exhibits great potential to create components for aerospace, biomedical, and energy applications with complex geometries and reduced material waste. Leveraging the unique solidification conditions inherent to AM, specifically selective laser melting (SLM), allows for site-specific microstructures. Nickel-based superalloys containing high volume fractions of γ’ are materials of choice for high-performance parts, however their use in SLM has proven challenging due to their tendency to form defects such as cracks during printing. There is thus a need for development of new alloys designed with the extreme thermal conditions of SLM in mind. We present a defect-resistant cobalt-nickel-based superalloy with a high γ’ volume fraction. As-printed microstructures resulting from various scan strategies and featuring cellular segregation due to high thermal gradients and interfacial solidification velocities will be presented as characterized via electron microscopy and electron backscatter diffraction. Implications for design of SLM specific alloys will be discussed.

High Throughput Material Characterization Framework for Additively Manufactured Graded Materials: Karthik Adapa1; Christopher Saldana1; Surya Kalidindi1; Thomas Feldhausen2; 1Georgia Institute of Technology; 2Oak Ridge National Laboratory
    The processing of functionally graded materials using laser-based additive manufacturing technologies has gained attention due to its applicability in the local tailoring of compositions within a component. However, the conventional mechanical testing methods have remained a bottleneck for probing the immense space developed by the material gradients because of their time-consuming and cumbersome nature. This paper proposes the Small Punch Test (SPT) as a high throughput mechanical testing method to produce reliable stress-strain curves and evaluate the constitutive behavior of the graded materials. The data obtained from micro-hardness and tensile correlated SPT tests are used to attain the structure-property characteristics for novel material compositions of graded stainless- steel and nickel superalloys. Solidification behavior and microstructures observed through electron microscopy and X-ray diffraction methods are validated against the CALPHAD based Scheil model simulations. The material characterization framework examined in this study proves an efficient path for developing and qualifying new materials.

High Performance Computing to Aid the Design of Novel Ti Alloys for Additive Manufacturing: Bala Radhakrishnan1; Tahany El-Wardany2; Ranadip Acharya3; 1Oak Ridge National Laboratory; 2Raytheon Technologies Research Center; 3Collins Aerospace Applied Research and Technology
    Additive manufacturing (AM) is significantly expanding the design space of structural alloy components through its ability to build-in geometrical features that are impossible through traditional manufacturing methods. However, because of the extreme thermal histories experienced during AM, it is necessary to design new alloy compositions that not only allow defect-free processing, but also exploit the AM processing conditions to promote unique microstructures to meet target properties. This research will highlight high-resolution, three-dimensional phase-field simulations of solidification microstructure development during AM of novel titanium alloys with emphasis on consistently achieving columnar-to-equiaxed transition (CET) to promote fine equiaxed grain structure formation throughout a component with complex geometrical features. Research sponsored by the Advanced Manufacturing Office of the U.S. Department of Energy under the High-Performance Computing for Energy Innovation (HPC4EI) program and performed at the Oak Ridge National Laboratory managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.

AM-based Combinatorial Approach for Site-specific Property Response: Soumya Nag1; Jaimie Tiley1; Ke An1; Raymond Unocic1; Jonathan Poplawsky1; 1Oak Ridge National Laboratory
    Currently, it can take several years to go from part concept to production on mission critical additively manufactured components, making broad adoption of this technology quite challenging. Also, for most conventional structural applications, a single alloy composition is used to fabricate the entire component, often compromising in terms of cost and/or performance. A pathway to make AM a substantial manufacturing strategy is to incorporate its unique attributes to fit site-specific performance needs. This is truly a material agnostic concept and may be employed to fabricate graded structural parts – namely using Ti alloys, Ni-base superalloys and Nb/Mo-based refractory alloys. Based on the above-mentioned alloy systems, the current study is a scientific deep dive on AM-based combinational alloy development strategy, geared towards generating hybrid microstructures for site-specific property response. The progress of this work will enhance capabilities to incorporate design optimization strategies and tailor multimodal AM fabrication into future applications.

Multi-metal 316L SS+Cu with Tailored Thermal Conductivity Manufactured via Laser Powder Bed Fusion: Saereh Mirzababaei1; V. Vinay Doddapaneni1; Kijoon Lee1; Chih-hung Chang1; Brian K. Paul1; Somayeh Pasebani1; 1Oregon State University
    Development of multi-metal with tailored thermal properties via additive manufacturing is investigated in this study. Ball milling of 316L and pure Cu powder followed by laser powder bed fusion process was adopted here. Thermal conductivity of additively manufactured coupons was experimentally measured using a laser flash method. The effect of porosity and volume fraction of Cu on effective thermal conductivity of the metal composite material was evaluated. Results revealed that porosity adversely affect the effective thermal conductivity of 316L+Cu metal composite. Effective thermal conductivity of metal composite increased with increasing volume fraction of Cu. For example, effective thermal conductivity of 316L matrix was enhanced by 250% at 300°C with addition of 60vol% Cu, without a significant sacrificing of mechanical properties, holding ~80% of microhardness of wrought 316L. Post processing such as hot isostatic pressing can improve the density and microstructure of samples, leading to higher enhancement in thermal conductivity (>500%).

Processing of Immiscible Iron-silver-materials via Laser Beam Melting: Jan Krüger1; Malte Dreyer1; Kay-Peter Hoyer1; Mirko Schaper1; 1Paderborn University
     Trace elements are well-suited for biomedical applications, as they offer natural substance uptake during degradation. Thus, iron-based alloys are promising due to their biocompatibility and adapted mechanical properties, but the degradation is insufficient. Previous approaches indicate increased degradation of iron with high manganese contents. Hence, efforts are required for the formation of noble phases promoting the cathodic dissolution of iron. By adding the antibacterial element silver, these phases can be created. As both elements are immiscible, it is feasible to manufacture this multi-material via laser beam melting (LBM). After degradation of the iron matrix, the remaining silver may cause undesirable complications, so that these phases must also be alloyed. Therefore, a moderate interaction between the matrix and the silver alloy is necessary to keep the alloy's properties.Thus, the correlation between alloying elements and process parameters regarding microstructure, degradation, mechanical properties, and biocompatibility is determined for iron(-manganese)-silver-multi-materials processed by LBM.

Design and Development of New Titanium Metastable Alloys for Use in Laser Powder Bed Fusion: Zou Zhiyi1; Minh-Son Pham2; Adam Clare1; James Murray1; Marco Simonelli1; 1University of Nottingham; 2Imperial College London
    In this study we present a new strategy to design and develop low-cost titanium metastable alloys for use in Laser Powder Bed Fusion (L-PBF). The work illustrates a computational methodology that integrates CALPHAD and empirical relationships to determine the stability of the β phase within a Ti-Sn-Cr system. We show how the methodology can be used to identify compositions that retain a full metastable β phase whilst minimising crack susceptibility. The predicted microstructural pathways are then validated by characterising the structure of buttons of corresponding alloys (derived from elemental shots) after re-melting with a L-PBF apparatus. This methodology allowed to isolate a low-cost Ti-7.5Cr-4Sn alloy which was prepared in powder format. Preliminary L-PBF experiments show the possibility to fabricate fully dense specimens that maintain strain-transformable attributes and a excellent strength-ductility relationship. Findings support a new strategy for the rapid development of new advanced titanium alloys for use in L-PBF.

Development of Al-Cu-Mg and Al-Mg-Si-Zr Alloys with Improved L-PBF Processability: Filippo Belelli1; Riccardo Casati1; Maurizio Vedani1; 1Politecnico di Milano
    Many Al alloys are susceptible to hot cracking when manufactured by Laser Powder Bed Fusion (L-PBF). In this study, small batches of Al powders were processed using a Reduced Build Volume device to target the optimal chemical composition of the alloy able to suppress hot cracks during solidification. Specifically, batches with increasing content of Cu and Zr were obtained through mechanical mixing of Al-4wt.%Cu-Mg and pure Cu and Al-Mg-Si and Al-Mg-Si-2wt.%Zr powders, respectively. The design strategy based on Cu relies on the segregation of an abundant Al-Al2Cu eutectic phase mixture during final stages of solidification, whereas the Zr addition promotes a fine equiaxed microstructure induced by heterogeneous nucleation of grains triggered by the precipitation of L12-Al3Zr crystal nuclei in the liquid phase. The design of the new alloys was supported by thermodynamic simulations. The microstructures and phase transformations of the alloys were investigated through electron microscopy, X-ray diffraction and differential scanning calorimetry.

Precipitation Strengthening Mechanism of a Ti-based Alloy Manufactured by Electron Beam Melting: Yujie Cui1; Kenta Aoyagi1; Kenta Yamanaka1; Tadashi Fujieda2; Akihiko Chiba1; 1Tohoku University; 2Hitachi Metals, Ltd.
     Although TiB particles possess good mechanical properties and high thermal stability, the precipitation strengthening effect of TiB particles is limited in the Ti-based alloys fabricated by conventional casting owing to the large size of TiB particles. Herein, the microstructure and mechanical properties of Ti-based alloys with boron addition fabricated by electron beam powder bed fusion (EB-PBF) were investigated. Compared with Ti-based alloys fabricated by conventionally casting or forging, the TiB particles was significantly refined in the alloy manufactured by EB-PBF. We verified that high cooling rate and solute segregation in the interface between TiB particle and matrix mainly accounted for the refinement of TiB precipitates. The Orowan strengthening and load-bearing strengthening caused by refined TiB particles mainly contributed to the enhanced strength of Ti-based alloy manufactured by EB-PBF. The research provides references for the manufacturing of materials strengthened by refined precipitates using additive manufacturing methods.

Preventing Mg Loss during Laser Powder Bed Fusion of an Al-Mg-Sc Alloy: Léa Deillon1; Felix Jensch2; Frank Palm3; Markus Bambach1; 1ETH Zürich; 2BTU Cottbus-Senftenberg; 3Airbus Central Research & Technology
    In Al-Mg alloys, precise control of the Mg content is essential to ensure predictable mechanical properties but Mg is commonly lost by evaporation and oxidation during thermal processing. In this study, we demonstrate the effectiveness of adding a low amount of Ca in preventing Mg losses during laser powder bed fusion of an Al-Mg-Sc alloy. After precipitation hardening, the new alloy - Calciscal®- shows a combination of high strength and good ductility owing to a fine-grained microstructure and the presence of numerous nano-sized precipitates. Moreover, the tensile properties are found to be very reproducible thanks to a better control and less variations of the Mg content. Transmission electron microscopy, electron backscattered diffraction and thermodynamic (equilibrium and out-of-equilibrium) predictions are combined to gain a better understanding of the complex microstructure that is formed during solidification and its subsequent evolution upon ageing, thus providing directions for further improvement of the composition.

Composition Control in Laser Powder Bed Fusion Additive Manufacturing through Differential Evaporation: Meelad Ranaiefar1; Edwin Schwalbach2; Ibrahim Karaman1; Raymundo Arroyave1; Alaa Elwany1; 1Texas A&M University; 2Air Force Research Laboratory
    Differential evaporation during part fabrication using laser powder bed fusion additive manufacturing can contribute to variation in composition. This uncontrolled evaporation is a prevalent issue throughout the additive manufacturing process and is associated with uncontrolled changes in structure and properties, along with the reduced performance of a part. However, we can utilize the underlying mechanisms of differential evaporation to direct processing parameters, control composition, tailor location-specific properties, and achieve desired performance. In this work, a model for predicting differential evaporation and the associated change in composition during laser powder bed additive manufacturing is presented. This is used to investigate the relationship between processing parameters, composition, and properties for an additively manufactured part.

Parameter Development and Fabrication of Test Parts of Bronze Alloy Cu-10Sn using Powder Bed Fusion (PBF): Michael Brand1; Robin Pacheco1; Colt Montgomery1; Ryan Mier1; 1Los Alamos National Laboratory
     Although bronze is one of the oldest alloys known to mankind, it is still has a variety of uses in many different applications. Beside artwork and musical instruments, bronze is of significant technological relevance in various applications including electrical connectors as well as high-precision springs and bearings. Thanks to excellent resistance to salt water corrosion, bronze is widely used in marine applications like propulsion and seawater handling systems. Using the EOS M290 complex shapes using complex materials can be fabricated by using the Powder Bed Fusion (PBF) process. Cu-10Sn bronze parameters will be developed as well density cubes and tensile bars will be fabricated. Porosity studies and mechanical properties obtained from parts fabricated by the conventional process will be compared to the mechanical properties of the additive manufactured parts.

Alloy Design for Additive Manufacturing: Bhaskar Majumdar1; 1New Mexico Institute of Mining and Technology
    In spite of major progress in additive manufacturing (AM), the high solidification rates and temperature gradient impose restrictions on the alloys that can be successfully processed without cracks and voids. Thus, many conventional high-performance alloys cannot be fabricated defect-free using AM. We use CALPHAD to rapidly screen through alloy additions without imposing large changes on conventional alloy compositions. The rationale is that such an approach may not require a large matrix of testing for insertion into actual applications. Examples include high-strength Al-alloys as well as Ni-base superalloys for high temperature applications. We will detail our rapid screening methodology and the use of experimental technique to the simulate rapid solidification conditions of AM, prior to fabrication of new alloy powders. Comparisons of theoretical results with experimental data will be provided.