Phase stability and mechanical properties of novel high entropy transition metal carbides

By Tyler J. Harrington, Joshua Gild, Pranab Sarker, Cormac Toher, Christina M. Rost, Olivia F. Dippo, C. McElfresh, Kevin Kaufmann, E. Marin, L. Borowski and 5 more. Acta Materialia, 2019

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Abstract Twelve different equiatomic five-metal carbides of group IVB, VB, and VIB refractory transition metals are synthesized via high-energy ball milling and spark plasma sintering. Implementation of a newly developed ab initio entropy descriptor aids in selection of candidate compositions for synthesis of high entropy and entropy stabilized carbides. Phase formation and composition uniformity are analyzed via XRD, EDS, S/TEM-EDS, and EXAFS. Nine of the twelve candidates form true single-phase materials with the rocksalt (B1) structure when sintered at 2473 K and can therefore be investigated as high entropy carbides (HECs). The composition (V0.2Nb0.2Ta0.2Mo0.2W0.2)C is presented as a likely candidate for further investigation as an entropy stabilized carbide. Seven of the carbides are examined for mechanical properties via nanoindentation. The HECs show significantly enhanced hardness when compared to a rule of mixtures average of the constituent binary carbides and to the highest hardness of the binary constituents. The mechanical properties are correlated to the electronic structure of the solid solutions, offering a future route to tunability of the mechanical properties of carbide ceramics via exploration of a new complex composition space.

Subfields: Aerospace Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/b517a0195296420b1b1c78def02af269399e0ea3

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Citations in the corpus

High-Entropy Ceramics (2019, background): “Following the work of the pioneers, a systematic study focused on the phase stability and mechanical properties of high-entropy carbides synthesized from group IV, V, and VI metal carbides [25] was carried out.”
Part I: Theoretical predictions of preferential oxidation in refractory high entropy materials (2020, background): “Prior research effort s in high entropy alloys (HEAs), summarized in references [2 , 7 , 8] , noted their improved mechanical properties.”
First-principles study, fabrication and characterization of (Zr0.25Nb0.25Ti0.25V0.25)C high-entropy ceramics (2019, positive): “At the early stage, only a couple of metal carbide CHCs, such as (Hf, Ta, Zr, Nb)C [8,9] and (Hf, Ta, Zr, Nb, Ti)C [10], were successfully synthesized and explored in experiment without the guidance from the ab-initio high-throughput computing.”
A high-entropy silicide: (Mo0.2Nb0.2Ta0.2Ti0.2W0.2)Si2 (2019, background): “rdness [17, 18, 19]; this line of work has further stimulated the subsequent development of high-entropy metal carbides as another class of UHTCs with increased hardness by a various groups worldwide [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]. Third, several other classes of high-entropy ceramics have”
From high-entropy ceramics to compositionally-complex ceramics: A case study of fluorite oxides (2019, background): “Since 2015, high-entropy ceramics (HECs) have been made in bulk form, including various high-entropy oxides [6–10], borides [11,12], carbides [13,14], nitrides [15], and silicides [16,17].”
Dual-phase high-entropy ultra-high temperature ceramics (2020, background): “It has already been shown by several independent studies that the single-phase HEB [21,37,62] or HEC [22,24] is harder than the rule-ofmixture (RoM) average of those of the five individual components (binary borides or carbides).”