High Entropy Alloys IX: Alloy Development and Properties: Poster Session
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; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical

Wednesday 5:30 PM
March 17, 2021
Room: RM 10
Location: TMS2021 Virtual

Atom-by-atom Understanding of Atom Probe Tomography of HEAs: Jiayuwen Qi¹; Christian Oberdorfer¹; Emmanuelle Marquis²; Wolfgang Windl¹; ¹The Ohio State University; ²University of Michigan
    Atom probe tomography (APT) is frequently used to examine homogeneity vs. phase separation in concentrated solid solutions (CSS). Since phase separation is often slow because of the stifled dynamics in CSS, high resolution is needed to identify even small nuclei of second phases. In order to quantify reconstruction fidelity and the size and composition limits to reliably identify phase nucleation in APT, we perform forward-simulation of virtual samples with a fully physical approach and determine resolution limits and artifacts from a comparison with the reconstructed sample. For that, we apply the TAPSim-MD approach to high entropy alloy tips, which combines a finite-element based solution for the electric-field with molecular dynamics in LAMMPS. This approach allows determining evaporation sequence and local structural effects for CSS samples, effective evaporation field changes from alloying, and reconstruction fidelity and artifacts by comparing conventional reconstruction of the simulated evaporation sequence to the original virtual sample.

Computation of Thermodynamics and Stability of FeNiCoCr(Mn/Pd) High Entropy Alloys: Competition between Equiatomic and Non-equiatomic: Nguyen-Dung Tran¹; Ying Chen¹; ¹Tohoku University
    High entropy alloy (HEA) represents a novel concept of alloy system in which multi-principle elements (at least 5) are mixed together in near-equiatomic proportions. Cantor HEA FeNiCoCrMn has been extensively studied due to its superior properties; and FeNiCoCrPd HEA has been recently synthesized and characterized, showing very good mechanical properties compared to the former. In this work, we systematically investigated the thermodynamics and stability of FeNiCoCr(Mn/Pd) HEAs and their subsystems from binaries to quinaries using integrated methods based on DFT. The electronic structures of the systems were analyzed, the contribution of different types of free energies including vibrational, thermal electronic, and entropy of mixing were calculated and highlighted, and the regularity of the dependence of stability on composition, e.g equiatomic vs. non-equiatomic, were found. Furthermore, our results predict the possibility of a wide range fluctuation in atomic fraction.

Fusion Plasma Relevant Erosion of Reduced Activation High Entropy Alloy-based lPasma-facing Material: Owais Ahmed Waseem¹; Kevin Woller¹; Faris Sweidan²; Ho Jin Ryu²; ¹Massachusetts Institute of Technology; ²Korea Advanced Institute of Science and Technology
    Reduced activation high-entropy alloy (HEA)-based material offers many benefits over pure W for future fusion plasma-facing applications. To evaluate the erosion behavior of a leading HEA-based material, W0.5(TaTiVCr)0.5, depth marker implantation and nuclear reaction analysis are used. A depth marker ~1.5痠 below the plasma-facing surface was implanted using 5.0 MeV F3+ ions and 3.2x1012 ions/cm2 fluence, the effects of implantation on the microstructure and mechanical properties of W0.5TaTiVCr were assessed using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and nanoindentation tests. Depth marker implantation, which developed pinholes and nanostructure on hot-rolled pure W, showed little to no modification of the microstructure of W0.5(TaTiVCr)0.5 under the present conditions. However, an increase of ~2.5 GPa in hardness of W0.5(TaTiVCr)0.5 was observed due to irradiation hardening. The plasma exposure of depth marker implanted W0.5(TaTiVCr)0.5 is being done for erosion analysis and will be presented in comparison to pure W.

High Throughput In Situ Micro-mechanical Testing of Multi-principal Element Alloy Thin Films to Enable Rapid Combinatorial Qualification: Robert Quammen¹; Paul F. Rottmann¹; ¹University of Kentucky
    Metals fabricated at the microscale (e.g. sputter deposited films) differ substantially in both properties and microstructure from their macroscale counterparts. For this reason, if the enticing properties of multi-principal element alloys (MPEAs) are to be realized for microscale applications (e.g. coatings, MEMS devices) specimens must be fabricated, characterized, and qualified at the microscale rather than extrapolating macroscale properties. Efficiently characterizing the vast and mostly experimentally unexplored compositional space of MPEAs to identify promising alloys is challenging with current test specimen fabrication techniques. In this work, freestanding, thin-film micro-mechanical testing specimens of combinatorially variable compositions and different loading modalities (tensile, compression, fatigue, indentation) were fabricated on a single wafer using a novel micro-fabrication process. In-situ micro-mechanical testing of these specimens was performed in combination with SEM characterization. Through the use of this procedure, candidate alloys for microscale applications can be verified and tested more efficiently.

Thermal and Corrosion Behaviour of Laser-Deposited High Entropy Alloys: Modupeola Dada¹; Patricia Popoola¹; Ntombizodwa Mathe²; Sisa Pityana²; Samson Adeosun³; Olufemi Aramide¹; ¹Tshwane University of Technology; ²Council for Scientific and Industrial Research; ³University of Lagos, Akoka
    In a previous study, the laser-deposited Cu-based and Ti-based High Entropy Alloys showed promising mechanical properties for aerospace applications after using preheating temperature at 400℃ as the laser parameter's optimization tool. Using the optimized laser parameters, this study examines the thermal behaviour and the corrosion responses of high entropy alloys in 3.5 wt.% H2SO4 solution at room temperature using a thermogravimetric analyzer and Potentiodynamic polarization, respectively. The influence of the laser processing parameter and the compositional variations of the high entropy alloys were investigated. The results showed that the high entropy alloys were thermally stable with an increase in laser power and energy density, the Cu-based laser-deposited high entropy alloy showed better corrosion resistance than the Ti-based laser-deposited high Entropy alloy and the conventional arc-melted Cu-based amalgams from literature.