Magnetics and the Critical Materials Challenge: An FMD Symposium Honoring Matthew J. Kramer: Microstructure and Processing
Sponsored by: TMS Functional Materials Division, TMS: Magnetic Materials Committee
Program Organizers: Scott McCall, Lawrence Livermore National Laboratory; Ryan Ott, Ames Laboratory

Monday 2:00 PM
February 28, 2022
Room: 210D
Location: Anaheim Convention Center

Session Chair: Orlando Rios, University of Tennessee-Knoxville

2:00 PM  Invited
Far-from-equilibrium Materials Processing: Jeffrey Shield¹; ¹University of Nebraska
    One approach to developing new materials, or optimizing existing materials, is by using far-from-equilibrium processing to create materials which are either metastable or difficult-to-obtain equilibrium phases. With respect to permanent magnet materials, two examples are MnAl and FeNi. Both relevant phases form in the L1₀ structure, but in MnAl the phase is metastable while in FeNi it is stable but difficult (impossible?) to form. In this paper, we will use inert gas condensation to produce nanoparticles in these and other alloys in order to produce magnetic materials. Modifying the plasma characteristics can promote either highly disordered structures, enabling diffusion or transitions to metastable or non-equilibrium phases, or in-plasma annealing that promotes atomic rearrangements in situ. Indications of L1₀ formation in FeNi have been observed in as-deposited Fe-Ni nanoparticles. In other alloy systems, the significant extension of solid solubility far beyond achievable by other processing methods provide pathways to new materials.

2:30 PM  Invited
From High-throughput Synchrotron Diffraction to Closed-loop Autonomous Materials Discovery: Ichiro Takeuchi¹; ¹University of Maryland
    Matt Kramer and I worked together with Apurva Mehta at SSRL during a crucial time when high-throughput diffraction of combinatorial libraries was being set up at SLAC as a semi-routine measurement technique. There is now a dedicated high-throughput measurement stage which can be readily mounted to several beamlines at SSRL. The largest credit naturally goes to Apurva, but the collaboration with Matt to screen for new permanent magnets was a big impetus to establish the measurement technique. This work has then led to a series of work where we perform machine learning analysis of large volumes of diffraction data. Our most recent effort is demonstration of closed-loop autonomous materials exploration and optimization (CAMEO). CAMEO can be used to navigate screening of combinatorial libraries performed at a synchrotron beamline, we have recently discovered a high-performance phase change memory material. This work is a collaboration with A. Gilad Kusne.

3:00 PM
Mechanically Strengthened Heterogeneous Sm-Co Sintered Magnets: Baozhi Cui¹; Xubo Liu¹; Cajetan Nlebedim¹; Jun Cui¹; ¹Ames Laboratory
     Samarium-cobalt sintered magnets have excellent magnetic properties, thermal stability, and corrosion resistance. They have been used in a variety of defense and civilian applications, particularly for applications between about 200 and 550慢, but the utilization of these materials is restricted by their brittleness. Improving their mechanical resilience would allow them to be more cost-effective, efficient, and robust for various function-related applications while reducing the pressure on critical material supply chains. In this work, we have engineered a series of novel heterogeneous microstructures, such as laminated coarser grain (CG) / finer grain (FG) or core/shell CG/FG microstructures, to achieve unprecedented combinations of superior mechanical and magnetic properties without altering the magnet compositions or the heat treatment procedures and parameters. A 60% enhancement of flexural strength was obtained in the heterogeneous Sm2(CoFeCuZr)17 sintered magnets, with negligible impact on their excellent magnetic properties. The technology is compatible with existing magnet manufacturing processes.

3:20 PM Break

3:40 PM
Utilizing High Energy X-rays to Perform In Situ observations of Alnico Spinodal Evolution: Emily Rinko¹; Matthew Kramer¹; Iver Anderson¹; ¹Iowa State University
    Rare earth (RE) free alnico permanent magnet (PM) alloys undergo spinodal decomposition of a solid solution B2 (BCC) phase to Fe-Co (α1), and Ni-Al-rich (α2) phases. As alnico’s coercivity largely relies on shape anisotropy, the distribution, size, and geometry of the resulting α1 impacts coercivity, which is too low for alnico to be an alternative to RE-PMs. Utilizing high energy X-rays with high time resolution (sub-second) small and wide-angle diffraction at different isothermal regions within the spinodal in controlled atmosphere, the evolution of the spinodal was studied in alnico alloys, one close to commercial alnico 8H and two others designed for higher coercivity. These observations helped provide improved understanding on how processing parameters impact the evolution of alnico’s spinodal and eventually can allow process optimization to promote maximum coercivity and energy product in alnico PMs. Funded by USDOE-OTT-TCF with EERE-VTO support and by KC-NSC through Ames Lab contract no. DE-AC02-07CH11358.

4:00 PM  Cancelled
Exploring the Edge of Stability in Chemically Complex Alloys: Pratik Ray¹; ¹IIT Ropar
    A number of critical materials and their alternatives showing promising physical properties in metastable states. This presents a compelling case for understanding the phase transformations at the edge of stability. Contrary to binary alloys and compounds, chemically complex materials offer an additional opportunity for controlling the phase transformation pathways – namely, through entropic stabilization. Such materials are heat-treatable leading to persistent metastable phases and microstructures. In this work, we look at three different systems – ZrHfNb, TiZrHfAl (both of which exhibit single phase metastable structures) and AlFeCoCrNi (which exhibits a transition from a single phase non-magnetic solid solution to a two phase structure including an AlNiCo rich phase which imparts the magnetic properties). The focus of this work lies in exploring the fundamentals of phase selection in complex systems using a combination of in-situ synchrotron diffraction and a novel machine learning paradigm.

4:30 PM  Invited
Synthesis and Characterization of Rare-earth-based Metallic Glasses: Yunus Kalay¹; Doguhan Sariturk¹; ¹Middle East Technical University
    Attributed to their unique mechanical and functional properties, nanocrystalline marginal metallic glass composites have attracted extensive research interest over the past years. Partial devitrification of the Al and Fe-RE (RE: rare-earth element) marginal metallic glasses results in anomalous nucleation rate of nanocrystals conflicting with the classical nucleation theory by several orders of magnitude. We’ve been working on revealing the root cause of nanocrystal formation through partial devitrification of metallic glasses for more than a decade. In this talk, we will talk about our long-term experimental and computational progress regarding synchrotron-based high energy X-ray diffraction (HEXRD), fluctuation and conventional electron microscopy, atom probe tomography (APT), and molecular dynamics (MD) studies on as-quenched, devitrified, and molten Al-RE based metallic glasses.