High Entropy Alloys IX: Alloy Development and Properties: Thermal and Other Properties
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
Thursday 2:00 PM
March 18, 2021
Room: RM 10
Location: TMS2021 Virtual
Session Chair: John Scully, University of Virginia; Gerald Frankel, The Ohio State University
2:00 PM Invited
Controlling the Corrosion Resistance of Multi-principal Element Alloys: John Scully1; Samuel Inman1; Angela Gerard1; Christopher Taylor2; Wolfgang Windl2; Daniel Schreiber3; Pin Lu4; James Saal5; Gerald Frankel2; 1University of Virginia; 2The Ohio State University; 3Pacific Northwest National Laboratory; 4Questek Innovations LLC; 5Citrine Informatics
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 more complex multiphase microstructures. Large ranges of material properties have been observed for MPEAs and mastery of the selection of elements and their compositions can enable novel combinations of properties not possible 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 energy associated with dissolution, can all be controlling factors governed by alloy composition and structure. These factors can mediate the electrochemical reactions controlling spontaneous corrosion. The quest for superior properties based on well-informed element choice 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) the behavior of elements in unusual combinations, and (c) the formation of complex protective oxides. These issues currently hold back progress in optimization of corrosion properties.
2:25 PM
Tracer Diffusion in Single Crystalline CoCrFeNi and CoCrFeMnNiHigh-entropy Alloys: Kinetic Hints towards a Low-temperature PhaseInstability of the Solid-solution?: Daniel Gaertner1; Josua Kottke1; Yury Chumlyakov1; Fabian Hergemöller1; Gerhard Wilde1; Sergiy Divinski1; 1Institute of Materials Physics, University of Münster
Tracer-diffusion of constituting elements in single-crystalline CoCrFeNi and CoCrFeMnNi is measured from 923 K to 1373 K. In CoCrFeMnNi, low-temperature deviations from otherwise linear Arrhenius-type dependencies are seen for all elements excluding Mn. The kinks are prominent at about 1100 K for Co and Ni and at 900 K for Cr and Fe indicating the existence of a low-temperature modification of the equiatomic solid-solution phase in CoCrFeMnNi. The temperature-dependent correlation factors of all elements are determined within the framework of the random alloy model providing insights into potentialmechanisms of the kinetic anomaly.
2:45 PM
Electron and Phonon Thermal Conductivity in High Entropy Carbides with Variable Carbon Content: Patrick Hopkins1; Christina Rost2; Trent Borman3; Mohammad Hossain3; Mina Lim4; Kathleen Quiambao-Tomko1; John Tomko1; Donald Brenner4; Jon-Paul Maria3; 1University of Virginia; 2James Madison University; 3Pennsylvania State University; 4North Carolina State University
The extreme level of chemical tunability make high entropy carbides (HECs) a significant materials platform for a variety of fundamental studies and functional applications. We investigate the thermal conductivity of high entropy carbide thin films as carbon stoichiometry is varied. The thermal conductivity of the HEC decreases with an increase in carbon stoichiometry, while the respective phonon contribution scales with elastic modulus changes as the excess carbon content increases. Based on the carbon content, the HECs transition from an electrically conducting metal-like material with primarily metallic bonding to a primarily covalently bonded crystal with thermal conductivities largely dominated by the phononic sub-system. Our results demonstrate the ability to tune the thermal functionality of high entropy materials through stoichiometries that dictate the type of bonding environment.
3:05 PM
Hyperbaric Laser Chemical Vapor Deposition of High-strength Aluminium-Silicon Carbide Nanocomposite Fibers: James Maxwell1; Avinash Baji1; Ben Mahler1; 1La Trobe University, EϵMC² Centre, Engineering Dept.
For this work, freestanding nanocomposite fibers were grown from mixtures of Bis(trimethylsilyl)methane and various organometallic and halide aluminum precursors. The resulting Al-Si-C fibers could be grown continuously to an arbitrary length—and were nanostructured due to the precursor pressures and laser powers employed. A variety of phases were found to be present, including aluminum carbide, silicon carbide, carbon, and silicon-rich phases. Scanning electron microscopy and Energy Dispersive X-ray Spectroscopy were used to characterize the composition and structure of the resulting materials. A map of the ternary phase diagram under these non-equilibrium conditions will be provided and discussed in detail. Hyperbaric laser chemical vapor deposition achieved high pressures and cooling rates sufficient for high growth rates and controlled, repeatable composition and nanostructure. Models for the growth of Al-Si-C and other nanocomposite fibers will be discussed.