A new type of compositionally complex M5Si3 silicides: Cation ordering and unexpected phase stability

Shivakumar, Sashank; Qin, Mingde; Zhang, Dawei; Hu, Chia-Ren; Yan, Qizhang; Luo, Jian

doi:10.1016/j.scriptamat.2022.114557

Cited by 15 publications

(4 citation statements)

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“…It is even more difficult to predict GB properties (and subsequently compute GB diagrams) for the diversifying classes of high-entropy ceramics (HECs) [66,67] and compositionally complex ceramics (CCCs), [66,[169][170][171][172], which have attracted substantial and exponentially growing research interests recently. GBs in high-entropy (and compositionally complex) oxides, [66,169,[172][173][174][175] borides, [176][177][178][179] carbides, [180][181][182] silicides, [183,184] and fluorides [185] with diversifying crystal structures and different bonding characters can possess exotic yet intriguing F I G U R E 15 Computing GB diagrams of thermodynamic and mechanical properties for Ga-doped Al. [64] (A) Validation of the computational approach by comparing an experimental STEM HAADF image with a simulated STEM image of an asymmetric Σ81 GB that best matches the experiment, based on the equilibrium atomistic structure obtained from hybrid MC/MD simulations.…”

Section: Discussionmentioning

confidence: 99%

“…It is even more difficult to predict GB properties (and subsequently compute GB diagrams) for the diversifying classes of high‐entropy ceramics (HECs) [ 66,67 ] and compositionally complex ceramics (CCCs), [ 66,169–172 ], which have attracted substantial and exponentially growing research interests recently. GBs in high‐entropy (and compositionally complex) oxides, [ 66,169,172–175 ] borides, [ 176–179 ] carbides, [ 180–182 ] silicides, [ 183,184 ] and fluorides [ 185 ] with diversifying crystal structures and different bonding characters can possess exotic yet intriguing thermodynamic and other physical properties. Understanding, predicting, and controlling the GBs in HEAs/CCCs and HECs/CCCs are of critical importance to enable us to attain their full technological potential.…”

Section: Discussionmentioning

confidence: 99%

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Computing grain boundary “phase” diagrams

Luo

2023

Interdisciplinary Materials

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Grain boundaries (GBs) can be treated as two‐dimensional (2‐D) interfacial phases (also called “complexions”) that can undergo interfacial phase‐like transitions. As bulk phase diagrams and calculation of phase diagram (CALPHAD) methods serve as a foundation for modern materials science, we propose to extend them to GBs to have equally significant impacts. This perspective article reviews a series of studies to compute the GB counterparts to bulk phase diagrams. First, a phenomenological interfacial thermodynamic model was developed to construct GB lambda diagrams to forecast high‐temperature GB disordering and related trends in sintering and other properties for both metallic and ceramic materials. In parallel, an Ising‐type lattice statistical thermodynamic model was utilized to construct GB adsorption (segregation) diagrams, which predicted first‐order GB adsorption transitions and critical phenomena. These two simplified thermodynamic models emphasize the GB structural (disordering) and chemical (adsorption) aspects, respectively. Subsequently, hybrid Monte Carlo and molecular dynamics atomistic simulations were used to compute more rigorous and accurate GB “phase” diagrams. Computed GB diagrams of thermodynamic and structural properties were further extended to include mechanical properties. Moreover, machine learning algorithms were combined with atomistic simulations to predict GB properties as functions of four independent compositional variables and temperature in a 5‐D space for a given GB in high‐entropy alloys or as functions of five GB macroscopic (crystallographic) degrees of freedom plus temperature and composition for a binary alloy in a 7‐D space. Other relevant studies are also examined. Future perspective and outlook, including two emerging fields of high‐entropy grain boundaries (HEGBs) and electrically (or electrochemically) induced GB transitions, are discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Computing grain boundary “phase” diagrams

Luo

2023

Interdisciplinary Materials

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“…HE or CC ceramics and silicides have been studied as single-phase materials, e.g., [69][70][71][72]. Single-phase materials are not considered in this paper.…”

Section: Introductionmentioning

confidence: 99%

On the Nb5Si3 Silicide in Metallic Ultra-High Temperature Materials

Tsakiropoulos

2023

Metals

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Refractory metal (RM) M5Si3 silicides are desirable intermetallics in metallic ultra-high temperature materials (UHTMs), owing to their creep properties and high Si content that benefits oxidation resistance. Of particular interest is the alloyed Nb5Si3 that forms in metallic UHTMs with Nb and Si addition. The choice of alloying elements and type of Nb5Si3 that is critical for achieving a balance of properties or meeting a property goal in a metallic UHTM is considered in this paper. Specifically, the different types of alloyed “normal” Nb5Si3 and Ti-rich Nb5Si3, namely “conventional”, “complex concentrated” (CC) or “high entropy” (HE) silicide, in metallic UHTMs with Nb and Si addition were studied. Advanced metallic UHTMs with additions of RMs, transition metals (TMs), Ge, Sn or Ge + Sn and with/without Al and with different Ti, Al, Cr, Si or Sn concentrations were investigated, considering that the motivation of this work was to support the design and development of metallic-UHTMs. The study of the alloyed silicides was based on the Nb/(Ti + Hf) ratio, which is key regarding creep, the parameters VEC and Δχ and relationships between them. The effect of alloying additions on the stability of “conventional”, CC or HE silicide was discussed. The creep and hardness of alloyed Nb5Si3 was considered. Relationships that link “conventional”, CC or HE bcc solid solution and Nb5Si3 in the alloy design methodology NICE (Niobium Intermetallic Composite Elaboration) were presented. For a given temperature and stress, the steady state creep rate of the alloyed silicide, in which TMs substituted Nb, and Al and B substituted Si, depended on its parameters VEC and Δχ and its Nb/(Ti + Hf) ratio, and increased with decreasing parameter and ratio value, compared with the unalloyed Nb5Si3. Types of alloyed Nb5Si3 with VEC and Δχ values closest to those of the unalloyed Nb5Si3 were identified in maps of alloyed Nb5Si3. Good agreement was shown between the calculated hardness and chemical composition of Nb5Si3 and experimental results.

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“…The high-entropy ceramics reported in recent years mainly include high-entropy disilicides, [2][3][4] high-entropy carbides, [5][6][7] high-entropy borides, [8][9][10] and high-entropy oxides. [11][12][13] Among them, high-entropy transition metal disilicides possess excellent oxidation resistance, 4,14,15 exceptional infrared emission properties, 3 good phase stability, 16 and high thermal expansion coefficient. 17 Gild and Qin et al almost simultaneously synthesized novel high-entropy silicides with excellent mechanical properties in 2019.…”

Section: Introductionmentioning

confidence: 99%

High‐entropy (Ti_0.2V_0.2Nb_0.2Mo_0.2W_0.2)Si₂ with excellent high‐temperature wear resistance

Li,

Chen,

Fan

et al. 2023

J Am Ceram Soc.

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The oxidation products (MoO3 and V2O5) have low melting points and tend to sublimate at high temperatures despite that MoSi2 and VSi2 may possess good self‐lubricating properties. To cope with this challenge, a high‐entropy transition metal disilicide was designed in this work in which transition metal elements that could form high melting point oxides were deliberately added. The high‐entropy (Ti0.2V0.2Nb0.2Mo0.2W0.2)Si2 (HE‐MSi2) with hexagonal structure was successfully prepared by SPS using Ti, V, Nb, Mo, W, and Si powders as the initial materials in this work. The HE‐MSi2 presents a high hardness (11.8 ± 0.4 GPa) and elastic modulus (387.2 ± 46.8 GPa). In particular, its hardness is higher than that of the corresponding disilicides. Noteworthy, HE‐MSi2 demonstrated superior wear resistance when compared to Mo‐Si‐based ceramics (such as MoSi2, Mo5Si3, and Mo5SiB2), high‐entropy carbides (such as (MoTaWVTi)C, (HfMoNbTaTi)C, and (TiVNbMoW)4.375, and traditional single‐phase ceramics (including Sialon, Si3N4, Al2O3, SiC, and ZrO2). Meanwhile, at a high temperature of 600°C, the friction coefficient and wear rate were reduced to 0.64 ± 0.05 and (1.88 ± 0.15)×106 mm3/N·m, respectively. The preferential oxidation of different elements of the HE‐MSi2 was validated through systematical characterization of composition evolution, which was dominantly impacted by high temperature and friction induction.

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A new type of compositionally complex M5Si3 silicides: Cation ordering and unexpected phase stability

Cited by 15 publications

References 47 publications

Computing grain boundary “phase” diagrams

Computing grain boundary “phase” diagrams

On the Nb5Si3 Silicide in Metallic Ultra-High Temperature Materials

High‐entropy (Ti_0.2V_0.2Nb_0.2Mo_0.2W_0.2)Si₂ with excellent high‐temperature wear resistance

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A new type of compositionally complex M5Si3 silicides: Cation ordering and unexpected phase stability

Cited by 15 publications

References 47 publications

Computing grain boundary “phase” diagrams

Computing grain boundary “phase” diagrams

On the Nb5Si3 Silicide in Metallic Ultra-High Temperature Materials

High‐entropy (Ti0.2V0.2Nb0.2Mo0.2W0.2)Si2 with excellent high‐temperature wear resistance

Contact Info

Product

Resources

About

High‐entropy (Ti_0.2V_0.2Nb_0.2Mo_0.2W_0.2)Si₂ with excellent high‐temperature wear resistance