Advances in Multi-Principal Elements Alloys X: Structures and Modeling: On-Demand Oral Presentations
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, Alcoa Technical Center
Monday 8:00 AM
March 14, 2022
Room: Advanced Materials
Location: On-Demand Room
Controlling Short-range Ordering to Simultaneously Enhance Strength and Ductility of High-entropy Alloys: Shuai Chen1; Zachary Aitken1; Subrahmanyam Pattamatta2; Zhaoxuan Wu2; Zhigen Yu1; David Srolovitz2; Peter Liaw3; Yong-Wei Zhang1; 1Institute of High Performance Computing; 2City University of Hong Kong; 3The University of Tennessee
We investigate two high-entropy alloys (HEAs), CoCuFeNiPd and CoCuFeNiTi, using a combination of Monte Carlo (MC) and molecular dynamic (MD) simulations. Our results show that CoCuFeNiPd exhibits much stronger short-range ordering (SRO) than CoCuFeNiTi. We find that it is the chemical-affinity disparity and exclusivity between Ti (Pd) with the remaining species that lead to the different SRO in these two HEAs. We also investigate the mechanical properties of CoCuFeNiPd HEA under different stages of SRO. Our results show that the SRO leads to a composite microstructure, consisting of three categories of clusters: low-energy clusters, medium-energy clusters, and high-energy clusters, with the medium-energy clusters playing the role as the matrix, the low-energy clusters serving as hard fillers to enhance the strength, while high-energy clusters acting as soft fillers to increase the ductility, resulting in the simultaneous increase in ultimate strength and ductility.
Interplay between Dislocations and Correlated Stress Environment in Random Alloys: Pierre-Antoine Geslin1; Ali Rida2; Enrique Martinez Saez3; David Rodney4; 1CNRS / INSA-Lyon; 2Johns Hopkins University; 3Clemson University; 4Univ Lyon 1
Solid solution strengthening is particularly important for the study and development of high entropy alloys. To investigate the influence of this solid solution on dislocation behavior, we first propose an elastic model of random alloys where atoms of different sizes are modeled as Eshelby inclusions. This allows to derive analytical expressions for the variance and the spatial correlations of the stress field that impedes dislocation motion. Surprisingly, we show that stress correlations are highly anisotropic despite the use of isotropic elasticity and the randomness of the alloy. Next, we use this correlated stress environment in a dislocation dynamics framework to derive the critical stress for dislocation depinning. We show that the stress correlations are crucial ingredients to predict accurately the magnitude of solid solution strengthening operating on screw and edge characters in these concentrated random alloys.
Mixing and Diffusion at Internal Interfaces in High Entropy Alloys: Gerhard Wilde1; 1University of Munster
High entropy alloys attract an increased attention as a potential structural material due to outstanding mechanical and physical properties. With this work, the self-diffusion kinetics of HEA that is critical concerning their phase stability and deformation behavior, particularly at elevated temperatures, shall be addressed shortly. Microstructural reasons for enhanced diffusion along specific internal interfaces, serving as short-circuits for atomic transport, will be discussed. Going beyond single high-entropy alloy behavior, intermixing possibilities of dissimilar high entropy alloys and the effect of co-deformation on microstructure evolution, particularly at the internal interfaces, will also be alluded to.
Understanding Chemical Short-range Ordering/Demixing Coupled with Lattice Distortion in Solid Solution High Entropy Alloy: Quanfeng He1; Yong Yang2; 1City University of Hong Kong; 2City University of Hong Kong
Chemical short-range ordering (CSRO) or demixing in solid solution high entropy alloys (HEAs) is a fundamental issue yet to be fully understood. In this work, we first developed a generalized quasi-chemical solid solution model that enables quantitative computation of the local chemical ordering or demixing in solid solution HEAs. After that, we performed synchrotron diffraction experiments, extensive Reverse Monte Carlo (RMC) simulations, and first principles calculations on the CoCrFeNi model alloy to study the development of local chemical environments after long time thermal annealing. The outcome of the combined research demonstrates that the development of local chemical ordering or demixing in CoCrFeNi is not only affected by the heat of mixing between dislike atoms but also coupled with local lattice distortion.
Mechanical Properties and Deformation Behavior of a Refractory Multiprincipal Element Alloy under Cyclic Loading: Jia Li1; Jing Peng1; Baobin Xie1; Li Li1; Yang Chen1; Yuanyuan Tian1; Fusheng Tan1; Qihong Fang1; Peter K. Liaw2; 1Hunan University; 2University of Tennessee
The refractory multiprincipal element alloys (RMPEAs) exhibit considerably high strengths at temperatures above 1,600°C, which can be a significant potential required in the high demand for aerospace applications. However, the atomic-scale work-hardening behavior of such important materials during low-cycle loading remains unknown. Here, we use atomic simulations combined with machine learning to study the low-cycle fatigue of nanocrystalline RMPEAs with different grain sizes, and obtain a large amount of data efficiently and accurately to reveal the cyclic deformation, work hardening, and damage mechanisms affected by grain size. An extensive grain growth is observed during the cyclic deformation, thus driving the dynamic Hall-Petch strengthening mechanism. Moreover, the present study reveals various cyclic deformation micro-mechanisms with different grain sizes, which can provide guidance for predicting the optimal grain size to achieve the best performance of low-cycle loading, and accelerating the development of superior fatigue-resistant RMPEAs.
Atomistic Simulations of Mechanical Responses and Defect Activities in B2 Low-to-high-entropy Intermetallic Compounds: Cheng-Yuan Tsai1; Chi-Huan Tung1; Shou-Yi Chang1; 1National Tsing Hua University
The defect activities and consequent mechanical responses of high-entropy intermetallic compounds with a high anti-phase boundary energy and a long-range ordered structure are worth investigations because of their complex configuration randomness and large lattice distortions. Hence in this study, the deformation of NiTi-based, ordered B2-phase high-entropy intermetallic compound was investigated by using molecular dynamics simulations, as compared to the behavior of low- and medium-entropy intermetallic compounds. The atomistic simulations showed that the low-entropy intermetallic compound proceeded with regular martensitic transformation, followed by the surface nucleation and catastrophic long-distance gliding of long dislocations at a very high applied stress. In comparison, with the complexity of atomic sizes and interatomic potential, the phase transition was suppressed. Instead, more homogeneous nucleation and smaller-range activities of abundant short defects took place at a low stress and led to the more uniform plastic deformation and higher work hardening rate of high-entropy intermetallic compounds.
Beyond Configurational Entropy: A Harmonic Multi-principal Elements Alloy: Zhaowei Wan1; Subramamyan Pattamatta1; Jian Han1; David Srolovitz2; 1City University of Hong Kong; 2The University of Hong Kong
High entropy alloys are substitutional solid solutions of multiple principal elements. “High entropy" refers to the high configurational entropy associated with randomly occupying lattice sites with different elements. The high strength of these alloys is associated with misfit stresses generated by random site occupancies. Here, we examine the effect of random misfit in a model system where bonds are harmonic and equilibrium bond lengths drawn from a Gaussian distribution. We demonstrate that harmonic lattices of single bond length atoms shrink upon heating (negative thermal expansion). We then demonstrate that bond length randomness is isomorphic to randomness associated with atomic vibrations. We exploit this “exact” analogy to determine the entropy associated with random misfit and show how to map between temperature and misfit randomness in the determination of lattice parameter and elastic constants. We exploit this approach to examine temperature-independent lattice parameters (invar) and elastic constant (elinvar) through misfit tuning.
High-throughput Ion Irradiation and Microstructural Characterization of Multi-principal-element Alloys: Michael Moorehead1; Benoit Queylat1; Phalgun Nelaturu1; Daniel Murray2; Mukesh Bachhav2; Dan Thoma1; Dane Morgan1; Adrien Couet1; 1University of Wisconsin-Madison; 2Idaho National Laboratory
Multi-principal-element alloys (MPEAs) have garnered interest in the nuclear community for their apparent resistance to microstructural damage under irradiation. While both experimentation and simulation have demonstrated reduced hardening and void swelling in MPEAs, the relationship between composition and irradiation response is still poorly understood since a rich experimental database for MPEAs does not yet exist. In this work, to accelerate the generation of experimental irradiation-response data for MPEAs, high-throughput synthesis, irradiation, and characterization techniques have been employed. Specifically, additive manufacturing has been used to produce arrays of various MPEAs (1-cm2 coupons), which have been subsequently irradiated using 4-MeV Ni2+ ions to a peak damage of 200 dpa at 500 °C. Hardening and void swelling have been assessed using nanoindentation and trenching via plasma focused ion beam (PFIB), respectively. Trends in the experimental data relating hardening and void swelling behavior to composition have been analyzed using different machine learning approaches.
High-throughput Mapping and Screening of Refractory High Entropy Alloy Property Space: Brent Vela1; Tanner Kirk2; Prashant Singh3; William Trehern1; Kadri Atli1; Raymundo Arroyave1; Ibrahim Karaman1; 1Texas A&M University; 2QuesTek Innovations LLC; 3Ames Laboratory
The continued development of gas turbine engines demands machinable low density materials capable of enduring temperatures exceeding 1000°C, creep, fatigue crack growth, and oxidation. Refractory High Entropy Alloys (RHEAs), alloys consisting of 4 or more refractory principal alloying components, have been proposed to meet these stringent operating requirements. However, the compositional complexity that endows these alloys with their unique properties also creates a combinatorically vast alloy space that is not easily explored. In this work we demonstrate an alloy design approach to identify regions of the RHEA design space that may meet performance constraints required in modern gas turbine engines. High-throughput CALPHAD, DFT, and analytical model calculations were performed to obtain alloy properties across the Al-Mo-Nb-Ta-V-W RHEA space, while t-distributed stochastic neighbor embedding (t-SNE) was used to visually map this property space. Alloys were filtered according to performance constraints and regions of feasibility were identified in this senary composition space.
Phase Field Modelling of Transformation Pathways and Microstructural Evolution in Multi-principal Element Alloys (MPEAs): Kamalnath Kadirvel1; Zachary Kloenne1; Jacob Jensen1; Shalini Koneru1; Hamish Fraser1; Yunzhi Wang1; 1Ohio State University
The refractory MPEA, AlMo0.5NbTa0.5TiZr, exhibits an interesting microstructure with ordered B2 phase being the matrix and a disordered bcc phase being the precipitate, unlike the conventional Ni-based superalloys where the ordered phase is the precipitate and the disordered phase is the matrix. It is crucial to understand the phase transformation pathways (PTPs) in these alloys in order to tailor the microstructure for specific engineering applications. In this work, we systematically investigated the possible PTPs in B2/bcc MPEAs through phase-field modelling. Our phase-field model (PFM) incorporates the phase-transformation processess such as order-disorder transitions, precipitation and spinodal decomposition. We studied the effects of volume fraction of individual phases, lattice misfit between the phases, modulus mismatch between the phases and the free energies of the individual phases on the microstructural evolution of these MPEAs. Our parameteric study can help in designing the alloy composition and heat-treatment schedule for tuning the microstructural features.
Cancelled
Unveil the Origin of Segregation-assisted Hardening in CoCrNi-alloys with Varying Mo Content Using Correlative TEM/APT Microscopy: Manuel Koebrich1; Daniel Hausmann1; Gernot Hausch2; Steffen Neumeier1; Mathias Göken1; 1Friedrich-Alexander-Universität Erlangen-Nürnberg; 2Dentalex
Correlative microscopy techniques as the combination of transmission electron microscopy (TEM) and atom probe tomography (APT) are capable of revealing deeper insights in segregation processes of solute alloying elements towards planar defects in low stacking fault energy alloys. Detailed knowledge concerning segregation effects therefore facilitates further tailoring of mechanical properties. This work investigates the secondary hardening mechanism by Mo-segregation in CoCrNi based systems, derivates of the commercial alloy MP35N (35Co-35Ni-20Cr-10Mo) with varying Mo content. This leads to an effect on the tensile strength after previous cold rolling due to the modification of the stacking fault energy. Secondary hardening, introduced by additional heat treatment, further improves the tensile strength up to 2400 MPa for the highest Mo content. Furthermore, TEM for characterization of observed planar defects and APT, to determine the local chemical composition were used highlighting the influence of elemental segregation on the mechanical properties.
Transformation Behavior and Superelasticity of TiZrHfNiCoCu Multi-component High-temperature Shape Memory Alloys: Izaz Rehman1; Tae-Hyun Nam1; 1Gyeonsang National University
Multi-component high-temperature shape memory alloys (HTSMAs) with nominal compositions of (TiZrHf)50Ni25Co10Cu15, (TiZrHf)50.5Ni24.834Co9.834Cu14.834, (TiZrHf)51Ni24.667Co9.667Cu14.667 and (TiZrHf)52Ni24.333Co9.333Cu14.333 (at.%) were prepared by arc-melting. Microstructures, transformation temperatures, phase constituents and superelasticity were investigated by scanning electron microscope observation, differential scanning calorimetery, X-ray diffraction and dynamic mechanical analysis in tensile mode, respectively. The microstructure of solution treated TiZrHfNiCoCu HTSMAs specimens consisted of (TiZrHf)(NiCoCu)-type matrix and (TiZrHf)2(NiCoCu)-type second phase. The area fraction of the second phase increased from 1.7% to 17.2% with the increased in (TiZrHf) content from 50 at.% to 52 at.%. Martensitic transformation start temperature of the solution treated specimens increased from 53.5 °C to 188.7 °C with the increase in (TiZrHf) content from 50 at.% to 52 at.%. TiZrHfNiCoCu HTSMAs showed clear superelasticity in the solution treated state. The superelastic recovery strain of solution treated TiZrHfNiCoCu HTSMAs was in the range of 4.2-4.6% depending on the alloy composition.
Novel Co-free Multi Principal Element Alloys (MPEAs) for Nuclear Applications: Computational Design and Experimental Evaluation: Dinesh Ram1; Gérard Ramstein2; Anna Fraczkiewicz3; Franck Tancret4; 1Université de Nantes, Institut des Matériaux de Nantes – Jean Rouxel (IMN), CNRS UMR 6502, Polytech Nantes, Rue Christian Pauc, BP 50609, 44306 Nantes Cedex 3, France & MINES Saint-Étienne, Centre SMS / LGF UMR CNRS 5307, 158, cours Fauriel, 42023 Saint-Étienne Cedex 2, France.; 2Université de Nantes, Polytech Nantes, UMR 6004 Laboratoire des Sciences du Numérique de Nantes, rue Christian Pauc, BP 50609, 44306 Nantes Cedex 3, France; 3MINES Saint-Étienne, Centre SMS / LGF UMR CNRS 5307, 158, cours Fauriel, 42023 Saint-Étienne Cedex 2, France.; 4Université de Nantes, Institut des Matériaux de Nantes – Jean Rouxel (IMN), CNRS UMR 6502, Polytech Nantes, Rue Christian Pauc, BP 50609, 44306 Nantes Cedex 3, France
Structural materials in nuclear environments, support heavy mechanical loads and less susceptible to corrosive and irradiation damages. Improved alloys are always expected and searched for. This work involves the computational design of precipitation hardened Co-free MPEAs with different reinforcing phases as observed Ni-based superalloys, with an objective of mechanical and stress-corrosion resistance at least equal to the latter group (e.g.: 718 grade), along with a superior tolerance to irradiation damage. Predictive models that co-relate composition, structure and properties were developed, using both machine learning and CALPHAD (Thermo-Calc). On this basis, multi-objective optimizations were set up on the Ni-Cr-Fe-Mn-Mo-Nb-W-Al-Ti system. Some alloys were selected from a set of Pareto-optimal compositions for fabrication and process optimization, as well as characterization of both microstructure (SEM, TEM, EDX) and mechanical properties (hardness, tensile test, high temperature compression). The new alloys exhibit satisfactory microstructure and mechanical behavior, in good agreement with predictions.