High Entropy Materials: Concentrated Solid Solutions, Intermetallics, Ceramics, Functional Materials and Beyond III: Processing and Properties
Sponsored by: TMS: Nanomaterials Committee
Program Organizers: Yu Zhong, Worcester Polytechnic Institute; Michael Gao, National Energy Technology Laboratory; Xingbo Liu, West Virginia University; Peter Liaw, University of Tennessee; Jian Luo, University of California, San Diego; Yiquan Wu, Alfred University; Mitra Taheri, Johns Hopkins University; Amy Clarke, Los Alamos National Laboratory
Monday 8:00 AM
October 10, 2022
Room: 324
Location: David L. Lawrence Convention Center
Session Chair: Martin Detrois, National Energy Technology Laboratory; Amy Clarke, Colorado School of Mines
8:00 AM Keynote
Do We Need a Refractory Alloy with Super-high Strength at Room Temperature?: Daniel Miracle1; S. Rao2; Oleg Senkov2; Carolina Frey3; 1Air Force Research Laboratory; 2Air Force Research Laboratory; MRL Materials Resources LLC; 3University of California Santa Barbara
Refractory complex concentrated alloys (RCCAs) are potential candidates for high-temperature (HT) structural applications beyond Ni-based superalloys. The number of publications on RCCAs is growing rapidly and many new RCCAs have been developed and reported. Although RCCAs are primarily targeted as for HT applications, many publications only report room temperature (RT) properties, and it is tempting to assume that alloys with very high RT strength may better retain strength at elevated temperatures. The purpose of this study is to explore this hypothesis. Our analysis shows no direct correlation between RT and HT strengths. Many RCCAs with RT strengths >1200 MPa lose strength rapidly above ~ 800-1000°C, and many of these alloys also have poor RT ductility. RCCAs that are ductile at RT and strong at HT generally have RT yield strengths ≤1200 MPa with a relatively weak temperature dependence. It is concluded from this analysis that RCCAs 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.
8:30 AM
Probing Short-Range Order and Its Effect on the Mechanical Properties of a CrCoNi Multi-principal Element Alloy Using Nanoindentation: Mingwei Zhang1; Qin Yu1; Dongye Liu2; Robert Ritchie1; Andrew Minor1; 1Lawrence Berkeley National Laboratory; 2University of California, Berkeley
Despite the success of directly imaging short-range ordering (SRO) in multi-principal element alloys (MPEAs) using energy-filtered TEM (EFTEM) and X-ray techniques, the effect of SRO on their mechanical properties have not been explored in detail. In the present study, we report on the results from nanoindentation experiments using quasi-static (QS) and nanoscale dynamic mechanical analysis (nanoDMA) loading conditions on CrCoNi samples with different thermomechanical treatments intended to generate different extents of SRO. Unlike the complementary uniaxial tensile experiments on bulk polycrystalline samples that show little difference in their mechanical properties, nanoindentation results exhibit a trend in pop-in loads generated by QS tests and yield strengths in quasi stress-strain curves generated by nanoDMA tests with an increasing amount of SRO. Our nanomechanical tests will be discussed in terms of complementary EFTEM characterization and implications of SRO on deformation plasticity in MPEAs.
8:50 AM
Production, Characterization, Mechanical Properties and Corrosion Resistance of CrCoNi-based Multi-principal Element Alloys: Francisco Coury1; Diego Santana1; Gustavo Bertoli1; David Silva1; Maria Eduarda Pablos1; Caroline Stoco1; Guilherme Koga1; Nicholas Birbilis2; João Pedro Oliveira3; Michael Kaufman4; Amy Clarke4; 1Universidade Federal de São Carlos; 2Australian National University; 3Universidade NOVA de Lisboa; 4Colorado School of Mines
Among the multi-principal element alloys (MPEA) developed to date, CrCoNi alloys have attracted a great deal of attention due to their good mechanical properties, especially the good combination of strength and toughness that some compositions can display. In this presentation, special focus will be given on three alloys non-equiatomic alloys derived from this system: Cr40Co40Ni20, Cr40Ni30Ni30 and Cr29.7Co29.7Ni35.4Al4.0Ti1.2. An in-depth characterization of these compositions will be shown together with their mechanical and electrochemical behaviors after different processing conditions. It will be shown the types of interfaces that can exist on the annealed and deformed alloys, the types of precipitates that can form and effective ways of characterizing them by electron microscopy. The deformation mechanisms, intrinsic mechanical properties and corrosion resistance will be discussed to critically evaluate the potential of these alloys in comparison to more conventional alloys.
9:10 AM
Revealing Phase Transformation and Deformation Behavior in a B2-base High-Entropy Alloy by In-situ Neutron Diffraction: Rui Feng1; Peter Liaw2; Ke An1; 1Oak Ridge National Laboratory; 2The University of Tennessee, Knoxville
Ordered intermetallic compounds have long been of interest as potential structural materials for use at elevated temperatures. In particular, B2 aluminides exhibit a wide range of interesting properties, such as high ordering temperature, corrosion resistance, and pseudo-elasticity effect. However, the lack of room-temperature ductility limits their applications due to an insufficient number of independent slip systems and poor grain-boundary (GB) cohesion. Recently, ductile multicomponent intermetallics have been achieved by the high-entropy alloy (HEA) concept. Here we design a B2-base HEA with a minor ductile face-centered-cubic (FCC) phase as a GB adhensive phase. The improved slip capability and stress-induced martensitic transformation of the multicomponent B2 phase are evidenced by in-situ neutron diffraction and transmission-electron microscopy. Together with the GB-strengthener, the tensile ductility of the designed alloy is enhanced to some extent. This work offers insights into alloy-design strategies that could improve the ductility of intermetallic alloys and accelerate their engineering applications.
9:30 AM Invited
Manufacturing of HEAs at Different Scales: Martin Detrois1; Michael Gao1; Paul Jablonski1; 1National Energy Technology Laboratory
The knowledge gained from melting and processing of high-entropy alloys (HEAs) at different scales is discussed with respect to melt parameters and characteristics. The melting techniques considered are button melting, vacuum induction melting (VIM) and electroslag remelting (ESR). While VIM produces HEAs with enhanced chemical homogeneity, particularly after being subjected to a homogenization heat treatment, and refined grain structure, other concerns arise from elemental contaminants associated with industrial-grade melt stock. Although ESR of the VIM product decreases the concentration of tramp elements, the narrow melt range typically found in HEAs or medium entropy alloys was found to decrease the melt efficiency. The experiments presented were performed on ingots ranging from 100 g to 75 kg.
9:50 AM Break
10:10 AM Invited
A Bayesian Approach to Efficiently Discover Refractory High Entropy Alloys: Raymundo Arroyave1; 1Texas A&M University
We present some recent advances in the development of frameworks to efficiently explore and exploit vast chemical-property spaces. Our framework relies on a Bayesian Optimization formalism to discover optimal materials under resource constraints. The framework employs multi-fidelity approaches, is capable of handling multiple objectives and constraints simultaneously, and can recommend multiple parallel queries at once. The framework is superior to traditional ICME approaches due to the capability of integrating experiments and simulations within a unified setting. It is also more efficient than combinatorial materials science approaches due to its iterative nature. The framework is deployed in the discovery of novel refractory high entropy alloys (RHEAs). While the optimization targets focus on mechanical performance, we also discuss some initial results, in which we evaluate the oxidation behavior as well as the performance of candidate alloys under 3D printing conditions. The framework is highly transferrable to other High Entropy Materials discovery problems.
10:40 AM
Thermodynamics and Phase Transformations in Refractory Complex Concentrated Superalloys: Eric Lass1; 1University of Tennessee-Knoxville
Refractory-based complex concentrated superalloys (CCSs) have received significant research attention in recent years because they show great promise as next-generation high temperature materials, supplanting conventional Ni-based superalloys which have reached their fundamental limits due to precipitate solvus and alloy melting temperatures. Such alloys are typically BCC, and may be strengthened by ordered B2 precipitates, leading to a two-phase microstructure that looks remarkably similar to their Ni-based cousins. However, the thermodynamics higher-order nature of the BCC-B2 transformation, compared to first-order for FCC-L12, leading to fundamental differences between the two systems. This presentation will explore how these differences affect microstructural development, such as the observed “inverted” B2-BCC structure. Design strategies to overcome such barriers to practical application are discussed from a thermodynamic perspective. Critical gaps in fundamental scientific understanding hindering future development CCSs are also discussed.
11:00 AM
Deformation Behaviors and Mechanisms 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; 5Oak Ridge National Laboratory; 6Kongju National University; 7The University of Tennessee, Knoxville
Single-phase solid-solution refractory high-entropy-alloys (RHEAs) show remarkable mechanical properties, such as high yield strength with significant resistance to softening at elevated temperatures. To understand the original of this high strength, it is important to investigate the deformation and strength mechanisms via an in-depth study. We have investigated the elastic- and plastic-deformation behaviors of two BCC NbTaTiV and NbTaTiVZr RHEAs, using both experiments and simulations. The in-situ neutron-diffraction results reveal that there is a transition in the load-bearing capability of the grains from isotropic to anisotropic 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 reason for high strengths in RHEAs.
11:20 AM
Design & Microstructural Evolution of Fe-rich, Co-Free Multi-principal Element Alloys: James Frishkoff1; Nathan Brown1; Madeline Rivera1; Kester Clarke1; Amy Clarke1; 1Colorado School of Mines
Multi-principal element alloys (MPEAs) are promising for demanding mechanical, thermal, corrosion and wear environments. Improved understandings of microstructural evolution with processing and deformation are prerequisite for the adoption of MPEAs in structural applications. Recrystallization, grain growth and precipitation kinetics are of particular relevance. In order to study these behaviors, a family of non-equiatomic, Fe-rich and Co-free precipitation-hardening MPEAs was designed through a multifactor screening approach. A design of experiment for thermomechanical processing and precipitation heat treatments is presented. Recrystallization, grain growth and precipitation kinetics are discussed and compared to existing ferrous alloy products.