Current Status of Research on the Oxidation Behavior of Refractory High Entropy Alloys

Gorr, Bronislava; Schellert, Steven; Müller, Frank; Christ, Hans‐Jürgen; Kauffmann, Alexander; Heilmaier, Martin

doi:10.1002/adem.202001047

Cited by 127 publications

(51 citation statements)

References 66 publications

(143 reference statements)

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“…A second prominent class of HEA systems are refractory high-entropy alloys (RHEAs), which comprise mostly refractory elements and invariably crystallize as body-centered cubic ( bcc ) solid solutions; these alloys have been considered as promising candidate materials for elevated-temperature applications due to their exceptional resistance to softening and extremely high melting points 9 – 11 . Although many practical challenges remain in the processing of RHEAs due to their brittleness and oxidation susceptibility 12 , numerous RHEAs have been designed, fabricated, and assessed experimentally, with additional insight coming from computational approaches 13 – 17 . Specifically, to investigate the deformation of RHEAs, transmission electron microscopy (TEM) studies on RHEAs have shown a dominant role of screw dislocations with increasing plastic strain 18 , 19 , and slip activity on high-order-planes has been observed through in situ scanning electron microscopy experiments 16 ; indeed, strong intrinsic lattice resistance has been generally found in these concentrated solid-solution alloys 19 , 20 .…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulations of dislocation mobility in refractory high-entropy alloys and the effect of chemical short-range order

et al. 2021

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Refractory high-entropy alloys (RHEAs) are designed for high elevated-temperature strength, with both edge and screw dislocations playing an important role for plastic deformation. However, they can also display a significant energetic driving force for chemical short-range ordering (SRO). Here, we investigate mechanisms underlying the mobilities of screw and edge dislocations in the body-centered cubic MoNbTaW RHEA over a wide temperature range using extensive molecular dynamics simulations based on a highly-accurate machine-learning interatomic potential. Further, we specifically evaluate how these mechanisms are affected by the presence of SRO. The mobility of edge dislocations is found to be enhanced by the presence of SRO, whereas the rate of double-kink nucleation in the motion of screw dislocations is reduced, although this influence of SRO appears to be attenuated at increasing temperature. Independent of the presence of SRO, a cross-slip locking mechanism is observed for the motion of screws, which provides for extra strengthening for refractory high-entropy alloy system.

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Section: Introductionmentioning

confidence: 99%

Atomistic simulations of dislocation mobility in refractory high-entropy alloys and the effect of chemical short-range order

et al. 2021

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“…The oxidation performance of NV2 in the three pest oxidation temperatures was significantly better than that of the RHEAs or RCCAs, even those that were rich in Al content [ 4 , 52 ]. The contamination of the phases in the diffusion zone and in the bulk is compared in Figure 17 .…”

Section: Discussionmentioning

confidence: 99%

The Effect of Fe Addition in the RM(Nb)IC Alloy Nb–30Ti–10Si–2Al–5Cr–3Fe–5Sn–2Hf (at.%) on Its Microstructure, Complex Concentrated and High Entropy Phases, Pest Oxidation, Strength and Contamination with Oxygen, and a Comparison with Other RM(Nb)ICs, Refractory Complex Concentrated Alloys (RCCAs) and Refractory High Entropy Alloys (RHEAs)

Vellios

Tsakiropoulos

2022

Materials

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In this work, the RM(Nb)IC alloy Nb–30Ti–10Si–5Cr–5Sn–3Fe–2Al–2Hf (NV2) was studied in the as-cast and heat-treated conditions; its isothermal oxidation at 700, 800 and 900 °C and its room temperature hardness and specific strength were compared with other Sn-containing RM(Nb)ICs—in particular, the alloy Nb–24Ti–18Si–5Cr–5Fe–5Sn (NV5)—and with RCCAs and RHEAs. The addition of Fe (a) stabilised Nbss; A15–Nb3X (X = Al, Si and Sn) and Nb3Si; metastable Nb3Si-m’ and Nb5Si3 silicides; (b) supported the formation of eutectic Nbss + Nb5Si3; (c) suppressed pest oxidation at all three temperatures and (d) stabilised a Cr- and Fe-rich phase instead of a C14–Nb(Cr,Fe)2 Laves phase. Complex concentrated (or compositionally complex) and/or high entropy phases co-existed with “conventional” phases in all conditions and after oxidation at 800 °C. In NV2, the macrosegregation of Si decreased but liquation occurred at T >1200 °C. A solid solution free of Si and rich in Cr and Ti was stable after the heat treatments. The relationships between solutes in the various phases, between solutes and alloy parameters and between alloy hardness or specific strength and the alloy parameters were established (parameters δ, Δχ and VEC). The oxidation of NV2 at 700 °C was better than the other Sn-containing RM(Nb)ICs with/without Fe addition, even better than RM(Nb)IC alloys with lower vol.% Nbss. At 800 °C, the mass change of NV2 was slightly higher than that of NV5, and at 900 °C, both alloys showed scale spallation. At 800 °C, both alloys formed a more or less continuous layer of A15–Nb3X below the oxide scale, but in NV5, this compound was Sn-rich and severely oxidised. At 800 °C, in the diffusion zone (DZ) and the bulk of NV2, Nbss was more severely contaminated with oxygen than Nb5Si3, and the contamination of A15–Nb3X was in-between these phases. The contamination of all three phases was more severe in the DZ. The contamination of all three phases in the bulk of NV5 was more severe compared with NV2. The specific strength of NV2 was comparable with that of RCCAs and RHEAs, and its oxidation at all three temperatures was significantly better than RHEAs and RCCAs.

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“…However, the addition of certain elements, such as Ti [ 154 ], Si [ 153 ], Cr [ 34 ] and Al [ 155 ], can significantly improve the oxidation resistance of RHEAs. During the oxidation process of W-containing RHEAs, complex oxidation products may be formed, having a significant impact on oxidation resistance [ 156 ]. How to improve the oxidation resistance is thus essential for the development and practical application of W-containing RHEAs.…”

Section: Functional Properties Of W-containing Rheasmentioning

confidence: 99%

Recent Advances in W-Containing Refractory High-Entropy Alloys—An Overview

Chen

Chen²,

Liu³

et al. 2022

Entropy

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During the past decade, refractory high-entropy alloys (RHEA) have attracted great attention of scientists, engineers and scholars due to their excellent mechanical and functional properties. The W-containing RHEAs are favored by researchers because of their great application potential in aerospace, marine and nuclear equipment and other high-temperature, corrosive and irradiated fields. In this review, more than 150 W-containing RHEAs are summarized and compared. The preparation techniques, microstructure and mechanical properties of the W-containing RHEAs are systematically outlined. In addition, the functional properties of W-containing RHEAs, such as oxidation, corrosion, irradiation and wear resistance have been elaborated and analyzed. Finally, the key issues faced by the development of W-containing RHEAs in terms of design and fabrication techniques, strengthening and deformation mechanisms, and potential functional applications are proposed and discussed. Future directions for the investigation and application of W-containing RHEAs are also suggested. The present work provides useful guidance for the development, processing and application of W-containing RHEAs and the RHEA components.

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Current Status of Research on the Oxidation Behavior of Refractory High Entropy Alloys

Cited by 127 publications

References 66 publications

Atomistic simulations of dislocation mobility in refractory high-entropy alloys and the effect of chemical short-range order

Atomistic simulations of dislocation mobility in refractory high-entropy alloys and the effect of chemical short-range order

Recent Advances in W-Containing Refractory High-Entropy Alloys—An Overview

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