Boron doped ultrastrong and ductile high-entropy alloys

Seol, Jae Bok; Bae, Jae Wung; Li, Zhi Ming; Han, Jong Chan; Kim, Jung Gi; Raabe, Dierk; Kim, Hyoung Seop

doi:10.1016/j.actamat.2018.04.004

Cited by 253 publications

(55 citation statements)

References 37 publications

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“…Ruhl and Cohen have found that most of the B in the Fe–Ni–B alloys is formed as precipitated (Fe,Ni) 3 B, which may be related to grain boundary strengthening in the Fe–Ni–Co–Al‐based alloy. In a recent study, Seol et al found that in the boron doped FeMnCrCoNi and Fe 40 Mn 40 Cr 10 Co 10 high entropy alloys that boron decorates the grain boundaries and acts twofold; 1) through interface strengthening and 2) grain size reduction. Although boron is widely used for improving the ductility in L1 2 ‐Ni 3 Al, L1 2 ‐Ni 3 Si, B2‐ordered FeAl, and L1 0 TiAl, due to its cohesive effect on the grain boundaries, precise control over the boron concentration is critical to exploit its beneficial effects.…”

Section: Introductionmentioning

confidence: 99%

“…Although boron is widely used for improving the ductility in L1 2 ‐Ni 3 Al, L1 2 ‐Ni 3 Si, B2‐ordered FeAl, and L1 0 TiAl, due to its cohesive effect on the grain boundaries, precise control over the boron concentration is critical to exploit its beneficial effects. Based on previous research for taking advantage of cohesion effect from boron, the amount of boron in the current study is 0.04% (atomic percent), which is 70 ppm in weight percent.…”

Section: Introductionmentioning

confidence: 99%

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Multifunctional Non‐Equiatomic High Entropy Alloys with Superelastic, High Damping, and Excellent Cryogenic Properties

et al. 2018

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A new class of non-equiatomic FeNiCoAlTaB (NCATB) high entropy alloy (HEA) is introduced, which exhibits tunable properties from cryogenic/ambient superelasticity to ultra-high strength through controlling the nature or type of martensite. In the current NCATB-HEA alloy system, depending on the size of γ'-Ni 3 Al (L1 2 ) precipitates, thin-plate, lenticular, butterfly, and lath-like martensite can form. When thin-plate thermoelastic martensite is favored, a superelastic strain of about 0.025 (ambient) and %0.01 (cryogenic) is achieved with a high yield stress of %800 MPa and a high-damping effect (10 times higher than Cu-Al-Ni superelastic alloy). While for butterfly and lath-like martensite dominated NCATB-HEA, an ultra-high yield stress of around 1.1 GPa is achieved while no superelasticity is demonstrated. This current alloy system helps to expand the application domain of HEAs, for example, into high-damping applications, robust actuators, space exploration, and other structural material applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multifunctional Non‐Equiatomic High Entropy Alloys with Superelastic, High Damping, and Excellent Cryogenic Properties

et al. 2018

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“…First, the yield strength is low due to the close packed fcc lattice structure. [19][20][21] Second, although the friction stress of these alloys is often higher than in pure metals or binary alloys, it is still usually too close to conventional structural alloys. This means that the level of lattice distortion currently exploited in most substitutional solid solution alloys does not contribute significantly to the yield strength.…”

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confidence: 99%

Ultrastrong Medium‐Entropy Single‐Phase Alloys Designed via Severe Lattice Distortion

et al. 2018

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thermomechanical processing routes which introduce high densities of dislocations and interfaces into materials. These defect populations introduce long-range stress fields, enabling substantial strengthening of materials. Thus, processing with the aim to introduce high densities of lattice defects into materials is a wellestablished and efficient method to enhance their strength. [12] Yet, when single-phase metallic materials have few defects such as in the recrystallized state and at the beginning of plastic yielding, they often have insufficient intrinsic lattice friction and thus low flow stress. [13,14] The lattice friction, quantified by the Peierls stress, is a measure of the resistance that an infinite straight dislocation has to overcome when moving from one potential valley to the next. The height of this energy barrier scales with the intrinsic atomic-scale lattice distortions and thus differs profoundly in nature from the long-range stress fields imposed by dense defect populations. In other words, the friction stress describes how severely dislocations are dragged as they move through the distorted Peierls potential landscape of massive solid solutions. In that respect, multiprincipal element solid mixtures, often termed high-or medium-entropy alloys (HEAs or MEAs), provide a very promising material design basis because each individual atom experiences a set of different neighbor atoms creating high and ubiquitous local lattice distortions and stresses. [15,16] In that context, multiprincipal element face-centered cubic (fcc) alloys have the potential for achieving an outstanding yield strength-ductility ratio as they naturally carry high inherent lattice distortions. [15,17,18] However, two key challenges have not been addressed in this context so far. First, the yield strength is low due to the close packed fcc lattice structure. [19][20][21] Second, although the friction stress of these alloys is often higher than in pure metals or binary alloys, it is still usually too close to conventional structural alloys. This means that the level of lattice distortion currently exploited in most substitutional solid solution alloys does not contribute significantly to the yield strength. [20,[22][23][24][25][26][27][28] Here, based on a combined theoretical and experimental approach, we show that the degree of lattice distortion is indeed a key parameter in controlling strengthening mechanisms for the design of hitherto unexplored ultrastrong medium-entropy single-phase alloys. For this purpose, we exploit vanadium (V) as a very efficient element in a Severe lattice distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium-and high-entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here it is shown that a simple VCoNi equiatomic medium-entropy alloy exhibits a near 1 GP...

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“…Thermodynamic parameters moderate diffusion temperature. Beyond that, the formation of boride compounds could be seen as it leads to a decrease in the Gibbs free energy [20,28,29].…”

Section: Elements (At%)mentioning

confidence: 99%

“…To strengthen HEAs with FCC solid solution phase, plenty of investigations have been reported concerning to address the problem: solid solution strengthening [14][15][16], nitriding [17], deformation strengthening [7,18] and annealing [19] are the methods have been used to strengthen this type of HEAs. In this study boron (B) as the minor alloying element has been selected due to following reasons; firstly, boron was nominated for its effective grain size reduction which was reported in various studies [20][21][22][23][24][25][26]. Secondly, the effects of thermomechanical treatments in the presence of boron were in a great deal of interest, and not last but least, the formation of possible M 2 B [27] and their effects on both microstructure and mechanical properties was supposed to investigate.…”

Section: Introductionmentioning

confidence: 99%

A novel medium entropy alloy based on iron-manganese-aluminum-nickel: influence of boron addition on phase formation, microstructure, and mechanical properties

Mohsen

2019

Mater. Res. Express

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A novel Medium Entropy Alloy (MEA) based on Fe-Mn-Al-Ni has been designed adopting High Entropy Alloys' (HEAs) phase formation rules, and the effects of minor boron addition on phase content and mechanical properties have been separately investigated. Boron-free Fe (52.71-x) Mn 31.11 Al 5.09 Ni 11.08 B x (x=0, 0.05, 0.2, 0.5, 0.7 wt%) MEA showed a single face-centered cubic (FCC) structure. XRD results indicated that with 0.05 and 0.2 wt% boron addition the system maintains its single-phase structure. Further boron addition led to the formation of metal boride intermetallics by the volume fractions of 4.6 and 6.1% of Fe 2 B intermetallic phase in as-cast and 2.7 and 5.4% in Deformed and Heat-treated (D&H) samples according to Rietveld analysis for 0.5 and 0.7 wt% boron doped alloys, respectively. Boron addition had a positive effect on grain size reduction of the system where just by 0.05 wt% boron addition the grain size has been almost halved compared to boron free as-cast sample. Moreover, it was observed that as the boron level increases, the hardness value increases. With in the all samples subjected to thermomechanical process, 0.7wt % boron doped alloy showed the best yield strength (increasing by ∼50%, from 151 MPa to 222.5 MPa) and ultimate tensile strength (increasing by ∼15%, from 476 MPa to 543 MPa) compared to undoped MEA at comparable ductility (ε>60%).

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Boron doped ultrastrong and ductile high-entropy alloys

Cited by 253 publications

References 37 publications

Multifunctional Non‐Equiatomic High Entropy Alloys with Superelastic, High Damping, and Excellent Cryogenic Properties

Multifunctional Non‐Equiatomic High Entropy Alloys with Superelastic, High Damping, and Excellent Cryogenic Properties

Ultrastrong Medium‐Entropy Single‐Phase Alloys Designed via Severe Lattice Distortion

A novel medium entropy alloy based on iron-manganese-aluminum-nickel: influence of boron addition on phase formation, microstructure, and mechanical properties

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