Advances in Multi-Principal Elements Alloys X: Alloy Development and Properties: Alloy Development and Application I
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical

Monday 8:30 AM
February 28, 2022
Room: 251A
Location: Anaheim Convention Center

Session Chair: Chanho Lee, Auburn University; Carl Koch, North Carolina State University

8:30 AM  Keynote
Low Density Multi-principal Element Alloys: A Review: Carl Koch1; 1North Carolina State University
    Structural materials with low densities and good mechanical properties have been sought after for many years. The new paradigm in alloy development/materials science of multi-principal element alloys offers greatly expanded possibilities for development of such alloys. For the purposes of this talk, “low density” will be defined as densities equal or less than about 6.0 g/cc. That is, for densities less than those of light weight steels and more comparable to commercial Ti or Al alloys. The limited number of studies from the literature on low density high entropy alloys will be briefly reviewed. A high throughput computational and experimental study directed by Intermolecular Inc. will be presented. Our group developed a fascinating alloy, Al20Li20Mg10Sc20Ti30 , which was prepared by ball milling of powders. The as-milled alloy exhibited a single phase fcc structure and had a remarkable hardness of about 6 GPa. This alloy will be discussed in some detail.

9:00 AM  Keynote
Design of Multi-principal Element Alloys for Use in a Broad Range of Temperatures: Cheng Zhang1; Enrique Lavernia2; 1University of California Irvine; 2National Academy of Engineering
    Dating back to an outstanding idea put forward in 2004, the past decade witnessed the emergence of multi-principal element alloys (MPEAs) where three or more elements are mixed equally or near equally into single- or multi-phase systems. The highly tunable properties of these alloys allow them to perform better than their conventional counterparts for critical structural applications, especially under extreme conditions. In this talk, the optimization of MPEAs’ properties at either low or high temperature ranges will be covered, and related strengthening and deformation mechanisms will be summarized. Moreover, the latest challenges and efforts for searching MPEAs that possess superb mechanical properties across a broad range of temperatures will be presented. Some unique temperature-dependent properties of MPEAs will also be described. In the end, guidance for future development of MPEAs at cryogenic-to-elevated temperatures will be provided.

9:30 AM  
Strengthening Mechanisms and Deformation Behaviors in Single BCC Phase Refractory High-entropy Alloys: Chanho Lee1; George Kim2; Yi Chou3; Michael Gao4; Ke An5; Gian Song6; Yi-Chia Chou3; Wei Chen2; Nan Li1; Saryu Fensin1; Peter Liaw7; 1Los Alamos National Laboratory; 2Illinois Institute of Technology; 3National Chiao Tung University; 4National Energy Technology Laboratory/Leidos Research Support Team; 5Oak Ridge National Laboratory; 6Kongju National University; 7The University of Tennessee
    Single-phase solid-solution refractory high-entropy-alloys (RHEAs) show remarkable mechanical properties, such as high yield strength with significant softening resistance at elevated temperatures. Hence, the in-depth study of the deformation behaviors for body-centered-cubic (BCC) RHEAs is a critical issue to explore the uncovered/unique deformation and strengthening mechanisms. We have investigated the elastic- and plastic-deformation behaviors of a single BCC NbTaTiV and NbTaTiVZr RHEAs, using integrated experimental efforts and theoretical calculations. The in-situ neutron-diffraction results reveal a transition of the elastic-deformation feature from isotropic to anisotropic modes at elevated temperatures. Furthermore, we have systematically and quantitatively determined lattice distortion using a theoretical model, first-principles calculations, synchrotron X-ray/neutron diffraction, and scanning-transmission-electron microscopy techniques. These results demonstrate that severe lattice distortion is a core factor for developing high strengths in RHEAs.

9:50 AM  Invited
Exploring Passivity of Multiple Principal Element Alloys: David Shifler1; 1Office of Naval Research
     The major factor controlling the corrosion of metals and alloys is the nature of the passive film in its environment. Ionic conductivity, electronic conductivity, surface reactivity or a combination of these three control the kinetics of passive film formation in traditional alloys with Al, Cr, Si, Ti, or Ta. TP Hoar suggested that superior passive films were the result of the formation of a non-crystalline film with short range order with bond flexibility. Multiple principal element alloys (MPEAs) opens new compositional spaces leading to millions of unexplored alloy possibilities. Rather than a primary element controlling passivity, how does a mixture of elements provide a basis for a passive film to form? How do these alloy configurational differences influence properties and behavior, and what variables control passivity? This requires establishment of new theories to explain and predict surface passivity of MPEAs. This promises to activate data-driven studies in MPEAs.

10:10 AM Break

10:30 AM  Invited
Toward High Throughput Design and Development of Multi-principal Element Alloys for Corrosion and Oxidation Resistance (MPEAs): Mitra Taheri1; 1Johns Hopkins University
    Multi-Principal Element Alloys (MPEAs) are the subject of emerging interest due to their compositional profile, which holds the promise of superior mechanical properties, high thermal stability, and high strength at high temperature. A clear challenge is harnessing MPEA composition and microstructure to realize the potential oxidation and corrosion resistance by producing a self-healing passivation layer. With millions of permutations of MPEAs in existence, however, it’s virtually impossible to nail down the “right” combination without innovation. This talk presents a combinatorial, high throughput approach to alloy discovery that enables assessment of thousands of MPEAs. Results for alloy systems that result from a combined theory and experiment effort reveal the benefit of such an approach to explore currently untapped compositional space toward alloy phase evolution and predict and control passivation/complex oxide evolution,

10:50 AM  Invited
Exploring Alloy Design Pathways for Beneficial Short-range Ordering: C. Tasan1; Feng He1; Hyun Oh1; Shaolou Wei1; James Lebeau1; Michael Xu1; 1Massachusetts Institute of Technology
    Short-range order (SRO) has been proposed in various alloys including complex concentrated alloys (CCAs), Fe-, Ti-, Cu-, Al-, Mg- based alloys, etc. However, beneficial utilization of SROs in the design of new alloys has been difficult, due to the lack of fundamental understanding of SRO as well as the absence of direct microscopic proof. The classical understanding of SRO, i.e., detrimental planar slip induced by SROs, does not do full justice to the complexity of this problem, as can be seen in recently developed CCAs and lightweight steels with unexpected improvements in mechanical properties while having planar slip mechanisms. Here, we aim to understand the dominant factors for SRO characteristics and the fundamentals of SRO-assisted deformation micromechanics directly observed by the RevSTEM technique, focusing on the SFE-SRO interactions in CCAs. This study will provide the guidelines for how to fabricate and manipulate the characteristics of SRO in alloys of interest.

11:10 AM  Invited
Additive Manufacturing of High-performance High-entropy Alloys: Wen Chen1; 1University of Massachusetts-Amherst
     High-entropy alloys (HEAs) are a class of multi-principal element alloys with high configurational entropy and severe lattice distortion. The radical departure from the conventional design motif has shifted the alloy design space from the corners of a phase diagram to the more spacious central region, which opens a new arena for explorations of new materials with new properties. Towards the widespread application of HEAs, the ability to manufacture them into geometrically-flexible components is necessary. Currently, HEAs are mainly processed by casting. Unfortunately, the highly concentrated HEA solid solutions often demonstrate a large solidification range that causes the inferior castability. To address this limitation, I will present some recent work in our group on additive manufacturing of HEAs, which enables the access of engineered hierarchical microstructures with excellent mechanical properties.