Advances in Multi-Principal Elements Alloys X: Alloy Development and Properties: Alloy Development and Application II
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 2:00 PM
February 28, 2022
Room: 251A
Location: Anaheim Convention Center

Session Chair: Joseph Poon, University of Virginia

2:00 PM  Cancelled
Do We Need a Refractory Alloy with Super-high Strength at Room Temperature?: Oleg Senkov1; Daniel Miracle1; 1Air Force Research Laboratory
    Refractory complex concentrated alloys (RCCAs) attract much attention as potential candidates for high-temperature (HT) structural applications. The number of publications on RCCAs is growing rapidly and many new RCCAs have been developed recently. Often only room temperature (RT) properties are reported, with the goal of developing RCCAs with high RT strength. However, RCCAs are intended for HT applications, and our analysis shows no direct correlation between RT and HT strengths. Many RCCAs with RT strength > 1200 MPa have poor RT ductility and lose their strength rapidly above ~ 800-1000C. RCCAs that are ductile at RT and strong at HT, generally have RT yield strength ≤ 1200 MPa and relatively weak temperature dependence of the yield strength. It is concluded from this analysis that refractory alloys intended for HT structural applications do not need to have super-high strength at RT. Details of this analysis will be provided in the presentation.

2:20 PM  Invited
What Controls Corrosion and Passivation of Compositionally Complex Alloys?: John Scully1; Samuel Inman1; Junsoo Han2; Debashish Sur1; Angela Gerard1; 1Department of Materials Science and Engineering- University of Virginia; 2Institut de Recherche Chimie Paris- Chimie ParisTech
    Multi-principal element alloys (MPEAs) offer the possibility of many degrees of freedom in the choice of alloying elements to produce either single phase solid solutions or complex multiphase microstructures. Mastery of element selection and alloy compositions can enable novel combinations of properties unobtainable in traditional alloys. From the aqueous corrosion perspective, optimization of phase stability, control of heterogeneities, passive film identity and its protectiveness, as well as substrate properties such as metal-metal bond strength and activation energies associated with dissolution, are controlling factors in corrosion resistance. The quest for superior properties based on well-informed choice of alloying elements is suggested as a path forward guiding MPEA formulations for corrosion performance. However, gaps in fundamental knowledge exist regarding (a) the specific functions of each element, (b) accounting for elements in unusual combinations, and (c) the formation of complex protective oxides. These issues currently hold back progress in optimization of corrosion properties.

2:40 PM  Invited
A Periodic Table for HEA Design: Scott Broderick1; Krishna Rajan1; Debasis Sengupta2; Stephen Giles2; 1University at Buffalo; 2CFD Research Corporation
    In this presentation, we provide an overview of the application of graph theory to the design of high entropy alloys (HEAs) based on the uncovering of 'hidden' chemical design rules. We capture the thermodynamic and structural complexity of HEAs and identify the potential existence of new combinations of phases not previously identified through tracking the connections in the network. We introduce a new series of indices for chemical substitution rules linking HEA composition, strength and ductility. The advantage of the network approach is that it incorporates numerous criteria for design (including mechanical and environmental properties, as well as microstructure) to identify HEA compositions when there are trade-offs between the various criteria. By mapping the high dimensional nature of the systematics of elemental data embedded in the periodic table into the form of a network graph, one can uncover the influence of specific combinations elements on engineering properties of HEAs.

3:00 PM  Invited
Data-guided Exploration of High Entropy Alloys for Cryocooler Applications: Indranil Roy1; Ankit Roy1; Ganesh Balasubramanian1; Louis Santodonato2; 1Lehigh University; 2Santo Science
    Closed-cycle helium gas refrigerators (cryocoolers), operating at an ultra-low temperature (down to 2K), rely on materials such as brass screens, Pb-alloy powder, and rare-earth alloy (e.g., Er3Ni). These materials serve as thermal regenerators which absorb and release heat during different phases of the refrigeration cycle. In recent years, the lack of rare-earth material supply has led to an urgent need for the discovery of new cryocooler materials with superior specific heats at low temperatures. High entropy alloys (HEAs) have shown promise mostly as structural materials, but hold potential for thermal applications at cryogenic temperatures. Here, we present results from a data-enabled approach towards the design of HEA compositions for high specific heat at extremely low temperatures.

3:20 PM Break

3:40 PM  
Additive Manufacturing of High-entropy Alloys for High Strength and Lightweight Structures: Jie Ren1; Wen Chen2; 1University of Massachusetts Amherst; 2University 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 corners of a phase diagram to more spacious central region, which opens a new arena for explorations of new materials with exceptional properties. Currently, HEAs are mainly manufactured by casting or through thermomechanical process. Although viable, such processing methods lose practical competency for manufacturing large-scale, especially geometrically-complex components. To address this limitation, I will present our recent work on additive manufacturing of HEAs for structural applications. These extreme printing conditions including large temperature gradients and fast cooling rates can result in far-from-equilibrium states which enable the access of engineered heterogeneous hierarchical microstructure ranging from nanometer to micrometer. The additively manufactured HEAs show simultaneously enhanced strength and ductility that open new opportunities for lightweight materials and structure design.