Additive Manufacturing: Materials Design and Alloy Development II: Alloy Design-High Temperature and Fe based Alloys
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Behrang Poorganji, Morf3d; James Saal, Citrine Informatics; Orlando Rios, University of Tennessee; Hunter Martin, HRL Laboratories LLC; Atieh Moridi, Cornell University

Wednesday 8:30 AM
February 26, 2020
Room: 6F
Location: San Diego Convention Ctr

Session Chair: Atieh Moridi, Cornell University


8:30 AM  Invited
Design of “Dynamic Alloys” for Additive Manufacturing: Jinyeon Kim1; Atieh Moridi1; 1Cornell University
    Despite numerous studies on additive manufacturing (AM) of different metallic alloys, the properties remain inferior to that of wrought or cast counterparts. Strong anisotropy due to the formation of columnar grains and processing induced defects are two major issues detrimentally influencing mechanical properties of AM parts. The aim of this research is to overcome these long-standing limitations of AM by designing novel “dynamic alloys”. In particular, we modify the stacking fault energy of high entropy alloys (HEAs). We study alloy compositions with different Fe and Mn content (i.e. FexMn80-xCr10Co10 (at.%, x=35, 40, 45)) where deformation mode changes from slip to twining induced plasticity and finally transformation induced plasticity. We investigate how the additional nucleation sites, e.g., twin boundaries and the interface between the austenitic and the martensitic phase contribute to in-situ microstructure refinement and crystallographic texture break down during the intrinsic heat treatment in AM process.

9:00 AM  
Hybrid Ti with High Work Hardening Rate and Ductile Martensitic Ti: Novel Alloy Concepts Delivered by Selective Laser Melting: Kenong Xia1; 1University of Melbourne
    Thanks to rapid cooling rates and small melt pool sizes, selective laser melting (SLM) can be used to create novel alloys difficult or impossible to achieve otherwise. Two examples are showcased to demonstrate the potential of such an innovative approach. First, a new strategy for producing future alloys with significantly enhanced performances was conceived through the hybridisation of different microstructures from existing alloys to generate a "composite of microstructures". A hybrid titanium from two existing alloys, one alpha/beta and one metastable beta, was designed and produced by SLM. An excellent combination of high strength, work hardening rate and ductility was achieved, superior to conventional Ti. In the second case, a fully martensitic alpha/beta alloy was shown to possess good ductility comparable to or better than the conventional counterpart. This novel approach can be applied to a vast variety of metals beyond Ti, heralding the coming era of microstructure-by-design.

9:20 AM  
High Entropy Alloy Design and Selection for Additive Manufacturing & Extreme Environment Applications: Emma White1; Duane Johnson; Nikolai Zarkevich1; Andrew Kustas2; Nicolas Argibay2; Michael Chandross2; Iver Anderson1; 1Ames Laboratory; 2Sandia National Laboratories
    Additive manufacturing (AM) is quickly penetrating the manufacturing community as a method of processing parts with complex part geometries and full assembly integration, especially of importance to applications in high temperature or harsh service environments. With the advent of the alternate kinetics inherent to the AM process, new alloy families amenable to rapid solidification, such as high entropy alloys (HEAs), become of great interest. Development of new AM-tailored alloys needs to be accelerated using computational models and validated via high-throughput experimental processes, to drastically shorten the time-to-market of AM. This work will describe the electronic structure modeling of HEA compositions, rapid, science-based alloy selection and experimental validation of the most promising chemistries, including the subsequent AM processing of the HEAs with the most desirable potential combination of properties. This work was funded by the U.S. Department of Energy’s - Energy Efficiency and Renewable Energy - Advanced Manufacturing Office.

9:40 AM  Cancelled
Alloy Design of Promising Highly Alloyed Metals by Using Elemental Powders in Laser Powder Bed Fusion: Simon Ewald1; Fabian Kies2; Johannes Schleifenbaum3; 1RWTH Aachen University - Digital Additive Production; 2RWTH Aachen University - Steel Institute; 3RWTH Aachen University - Digital Additive Production, Fraunhofer Institute for Laser Technology
    The design of new alloys by and for metal Additive Manufacturing (AM) is an emerging field of research. Currently, pre-alloyed powders are used in metal AM, which are expensive and inflexible in terms of varying the chemical composition. In the present study powder mixtures are used for agile and resource efficient designing and screening of new alloys. This method was evaluated on the new and chemically complex materials group of multi-principal element alloys, also known as high-entropy alloys. First, process parameters for processing powder blends containing at least five different elemental powders were developed. Second, the influence of processing parameters and the resulting energy input on the homogeneous distribution of the elements were investigated. Microstructural characterization was carried out by optical microscopy, EBSD and EDS, while mechanical properties were evaluated using tensile testing. Finally, the applicability of powder blends in LPBF was demonstrated by manufacturing geometrically complex lattice structures.

10:00 AM  
Laser Powder Bed Fusion of a CoNi-base Superalloy for Advanced Components in Extreme Environments: Kira Pusch1; Sean Murray1; Andrew Polonsky1; Chris Torbet1; Peeyush Nandwana2; Michael Kirka2; Ryan Dehoff2; Ning Zhou3; Stephane Forsik3; William Slye3; Tresa Pollock1; 1University of California, Santa Barbara; 2Oak Ridge National Laboratory; 3Carpenter Technology
    The geometric flexibility afforded by additive manufacturing enables the possibility of complex component designs for advanced materials in extreme environment applications. However, many of the high-performance gamma prime-containing nickel-base superalloys, used for instance in critical components of the hot section of turbine engines, are not easily processed via additive technologies due to their tendency to crack upon solidification. Parts fabricated by laser powder bed fusion (LPBF) are especially prone to cracking due to high thermal gradients and solidification velocities characteristic of the process. Here we present the development of a novel CoNi gamma prime-containing superalloy with inherent oxidation resistance and high gamma prime solvus temperature that is amenable to processing via LPBF. Microstructure development in the as-deposited as well as heat treated state will be discussed, as well as the mechanical properties of these alloys in comparison to other gamma prime-containing superalloys currently under investigation.

10:20 AM Break

10:35 AM  Keynote
ICME-based Design of γ’-strengthened Co-based Superalloys for Additive Manufacturing: Eric Lass1; Michael Katz2; Richard Ricker2; 1University of Tennessee, Knoxville; 2National Institute of Standards and Technology
    Two-phase γ-γ’ Ni-based superalloys are of significant interest for use in additive manufacturing (AM) applications. Unfortunately, the properties of most Ni-based superalloys are not conducive to AM processing, such as inherently large solidification temperature ranges, microsegregation, and γ’ precipitation behavior, all of which can lead to cracking during AM processing and other issues. Over the last decade, Co-based superalloys with an analogous two-phase γ-γ’ microstructure have been discovered, investigated and developed. This new class of superalloys exhibit properties that are more amenable to AM processing than their Ni-based counterparts including significantly narrower freezing ranges and minimal solidification microsegregation. This work uses an Integrated Computational Materials Engineering approach in designing Co-based superalloys with intriguing properties for use in AM applications. Calphad-based thermodynamic and kinetic models are employed to quantify microstructural stability, solidification and precipitation behavior, and other properties. Selected alloys are characterized experimentally for their potential as AM materials.

11:05 AM  
Understanding Microstructure Development of Additively Manufactured Ni-based Superalloys by Combining In-situ/Ex-situ Characterization and Computational Modeling: Jonah Klemm-Toole1; Alec Saville1; Chandler Becker1; Benjamin Ellyson1; Yaofeng Guo1; Chloe Johnson1; Brian Milligan1; Andrew Polonsky2; Kira Pusch2; Kester Clarke1; Niranjan Parab3; Kamel Fezzaa3; Tao Sun3; Damien Tourret4; Tresa Pollock2; Amy Clarke1; 1Colorado School of Mines; 2University of California Santa Barbara; 3Advanced Photon Source; 4IMDEA Materials Institute
    Additive manufacturing unlocks the possibility of producing highly complex metallic structures with location and orientation specific properties. In order to control microstructure and crystallographic orientation during solidification, a comprehensive understanding of the thermal gradients and solidification velocities and their impact on the solidification process must be developed. Single crystals of model Ni-based superalloys with controlled crystallographic orientations were laser melted, while obtaining in-situ x-ray radiography to directly measure the velocity of the solid-liquid interface. These results are used to inform complementary computational models used to estimate thermal gradients. Ex-situ microscopy was performed to characterize the microstructure after solidification. Current solidification theories are invoked to relate the measured solidification velocities and thermal gradients to the observed morphology and crystallographic texture after solidification. By combining in-situ/ex-situ characterization and computational modeling of the solidification process, new insights have been developed into the microstructural and crystallographic texture evolution in additively manufactured Ni-based superalloys.

11:25 AM  
Understanding Printability of Steels from Computational Modeling of Microstructural Evolution: Jiayi Yan1; Hamed Ravash1; Martin Walbrühl1; Ida Berglund1; 1QuesTek Europe AB
    Hot cracking is a major problem associated with additive manufacturing (AM) of many steels. In order to understand hot cracking susceptibility specific to materials and processing for materials design, it is critical to accurately predict the nonequilibrium kinetics of solidification and solid-solid phase transformations during AM. In this presentation we demonstrate how Scheil and DICTRA simulations and Thermo-Calc Property Models can be applied to predict the nonequilibrium microstructure during AM in some tool steels and stainless steels. Microstructure-specific materials properties, for example thermal expansion, can be obtained with the support of necessary databases. The capabilities and limitations of the computational tools are discussed, and directions of development are suggested.

11:45 AM  
Site-specific Alloying of Low Carbon Steel Through Binder Jet Additive Manufacturing: Karl Davidson1; Po-Ju Chiang1; Lihua Zhao2; Matteo Seita1; 1HP-NTU Digital Manufacturing Corporate Lab; 2HP Labs for 3D Printing and Digital Manufacturing
    Binder jet additive manufacturing (BAM) enables mass production of near-net-shape parts with minimal post processing requirements for a range of industries and applications. One additional advantage of BAM over other metal additive modalities is the ability to tailor the alloy composition—and thus the local microstructure—of the fabricated parts by employing multiple binders with different alloying elements. In this proof of concept work, we emulate the BAM process using press-bar samples of low carbon steel powders with location-specific deposition of a carbon-containing agent. By controlling the sintering process of the preforms, we produce samples with site-specific microstructures, which exhibit variable microhardness values in accordance with the carbon content. Our results indicate the possibility of using BAM to fabricate parts with topology optimised microstructures.