Development of Precipitation-Strengthened Al0.8NbTiVM (M = Co, Ni) Light-Weight Refractory High-Entropy Alloys

Single-phase solid-solution refractory high-entropy alloys (RHEAs) have been receiving significant attention due to their excellent mechanical properties and phase stability at elevated temperatures. Recently, many studies have been reported regarding the precipitation-enhanced alloy design strategy to further improve the mechanical properties of RHEAs at elevated temperatures. In this study, we attempted to develop precipitation-hardened light-weight RHEAs via addition of Ni or Co into Al0.8NbTiV HEA. The added elements were selected due to their smaller atomic radius and larger mixing enthalpy, which is known to stimulate the formation of precipitates. The addition of the Ni or Co leads to the formation of the sigma precipitates with homogeneous distribution. The formation and homogeneous distribution of sigma particles plays a critical role in improvement of yield strength. Furthermore, the Al0.8NbTiVM0.2 (M = Co, Ni) HEAs show excellent specific yield strength compared to single-phase AlNbTiV and NbTiVZr RHEA alloys and conventional Ni-based superalloy (Inconel 718) at elevated temperatures.

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The Temperature Dependence of Deformation Behaviors in High-Entropy Alloys: A Review

Metals ◽

10.3390/met11122005 ◽

2021 ◽

Vol 11 (12) ◽

pp. 2005

Author(s):

Pengfei Wu ◽

Kefu Gan ◽

Dingshun Yan ◽

Zhiming Li

Keyword(s):

Single Phase ◽

Elevated Temperatures ◽

High Entropy Alloys ◽

Alloy Development ◽

Temperature Dependent ◽

High Entropy ◽

The Past ◽

Different Temperatures ◽

Deformation Behaviors ◽

Environmental Temperatures

Over the past seventeen years, deformation behaviors of various types of high-entropy alloys (HEAs) have been investigated within a wide temperature range, from cryogenic to high temperatures, to demonstrate the excellent performance of HEAs under extreme conditions. It has been suggested that the dominated deformation mechanisms in HEAs would be varied with respect to the environmental temperatures, which significantly alters the mechanical properties. In this article, we systematically review the temperature-dependent mechanical behaviors, as well as the corresponding mechanisms of various types of HEAs, aiming to provide a comprehensive and up-to-date understanding of the recent progress achieved on this subject. More specifically, we summarize the deformation behaviors and microscale mechanisms of single-phase HEAs, metastable HEAs, precipitates-hardened HEAs and multiphase HEAs, at cryogenic, room and elevated temperatures. The possible strategies for strengthening and toughening HEAs at different temperatures are also discussed to provide new insights for further alloy development.

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Modeling the Microstructural and Yield Strength Evolution of an Age-Hardenable Al Alloy for High Temperature Applications

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.380 ◽

2016 ◽

Vol 879 ◽

pp. 380-385 ◽

Cited By ~ 1

Author(s):

Marco Colombo ◽

Elisabetta Gariboldi ◽

Paola Bassani ◽

Mihaela Albu ◽

Ferdinand Hofer

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Yield Strength ◽

Elevated Temperatures ◽

Age Hardening ◽

Homogeneous Distribution ◽

Al Alloy ◽

Physically Based ◽

The Matrix ◽

Physically Based Models

The mechanical properties of Al alloys are strongly affected by their microstructure: the size and shape of precipitates, their homogeneous distribution and their coherency with the matrix are of primary importance for an effective strengthening of the alloys at room and elevated temperatures. Physically-based models are powerful tools to predict the influence of the mentioned parameters on the mechanical properties of the alloy after age hardening, and also to predict the effect of high temperature service conditions on microstructure evolution. Scope of this work is to model the dimensional kinetic evolution of plate shaped precipitates of an Al-based alloy during aging and after different overaging times at elevated temperature, and use these results to estimate the alloy yield strength. The alloy strengthening response is due to three terms, linearly summed: the intrinsic strength of Aluminum, the contribution from solute in solid solution and the contribution arising from precipitates. The consistency of the model is verified with experimental data obtained from a 2014 Al alloy.

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Microstructure and Mechanical Properties Investigation of New Al10Cr12Mn28Fe(50-x)Ni(x) High Entropy Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.998.9 ◽

2020 ◽

Vol 998 ◽

pp. 9-14

Author(s):

Ahmed W. Abdel-Ghany ◽

Sally Elkatatny ◽

Mohamed Abdel Hady Gepreel

Keyword(s):

Mechanical Properties ◽

Yield Strength ◽

Compressive Yield Strength ◽

High Entropy Alloys ◽

High Ductility ◽

Cast Material ◽

High Entropy ◽

Arc Melting ◽

Microstructure And Mechanical Properties ◽

Cast Alloys

In the present study, two newly developed non-equiatomic high entropy Al10Cr12Mn28Fe(50-x)Ni(x) alloys (x= 20 & 15 at%, namely: Ni20 & Ni15, respectively) are investigated. The studied HEAs were designed based on thermodynamic principles to maintain high ductility and improve strength. Ingots were prepared using arc-melting then microstructure examinations and mechanical properties for the as-cast alloys were done. The mechanical properties were enhanced for the as-cast material, compared with previously introduced HEAs of the same system, namely Al5Cr12Mn28Fe35Ni20, (Al5) and Al10Cr12Mn23Fe35Ni20, (Al10). Al10Cr12Mn28Fe30Ni20 (Ni20) HEA generally shows the highest compressive yield strength which was improved by ∼7% when compared with previously introduced Al10.

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High-entropy alloys in light transition metal systems

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314090561 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C943-C943

Author(s):

Roksolana Kozak ◽

Walter Steurer

Keyword(s):

Single Phase ◽

Elevated Temperatures ◽

High Hardness ◽

High Entropy Alloys ◽

X Ray Diffraction ◽

High Entropy ◽

Mixing Entropy ◽

Al Content ◽

New Class ◽

Arc Melting

High-entropy alloys (HEAs) are a new class of alloys designed with the approach of maximization of configurational mixing entropy by increasing the number of constituents [1,2]. Alloys produced in such a way are reported for a variety of promising properties (high hardness and strength, wear resistance, magnetism etc.) [3]. However, origin of these properties (microstructure, phase content, element composition, thermal history) is not always clear. High mixing entropy in HEAs favours the formation of single-phase substitutional solid solutions at elevated temperatures with approximately equiatomic compositions and simple average crystal structures of either the cF4-Cu (fcc) or the cI2-W (bcc). Nevertheless, only a few element combinations produce truly single-phase materials. In order to search for new HEAs compositions samples in the systems Cr-Fe-Co-Ni-Al and Cr-Fe-Co-Ni-Mn were synthesized by arc melting and homogenized in tantalum ampoules at 1100 and 1300 °C for 2 weeks. DTA, X-ray diffraction and electron microscopy measurements were performed. Only samples with small Al content (~ 5 at.%) showed the single-phase microstructure. Their local atomic structure is under investigation.

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High-entropy alloys: Structure, mechanical properties, deformation mechanisms and application

Izvestiya Ferrous Metallurgy ◽

10.17073/0368-0797-2021-4-249-258 ◽

2021 ◽

Vol 64 (4) ◽

pp. 249-258

Author(s):

K. A. Osintsev ◽

V. E. Gromov ◽

S. V. Konovalov ◽

Yu. F. Ivanov ◽

I. A. Panchenko

Keyword(s):

Mechanical Properties ◽

Phase Composition ◽

Yield Strength ◽

High Strength ◽

Mechanical Tests ◽

High Entropy Alloys ◽

High Entropy ◽

Temperature Range ◽

Deformation Curves ◽

Fcc Lattice

The article considers a brief review of the foreign publications on the study of the structure, phase composition and properties of five-component high-entropy alloys (HEAs) in different structural states in a wide temperature range over the past two decades. HEAs attract the attention of scientists with their unique and unusual properties. The difficulties of comparative analysis and generalization of data are noted due to different methods of obtaining HEAs, modes of mechanical tests for uniaxial compression and tension, sizes and shapes of the samples, types of thermal treatments, and phase composition (bcc and fcc crystal lattices). It is noted that the HEA with a bcc lattice has mainly high strength and low plasticity, and the HEA with a fcc lattice has low strength and increased plasticity. A significant increase in the properties of the FeMnCoCrNi HEA with a fcc lattice can be achieved by alloying with boron and optimizing the parameters of thermal mechanical treatment at alloying with carbon in the amount of 1 % (at.). The deformation curves analyzed in the temperature range –196 ÷ 800 °C indicate an increase in the yield strength with a decrease in the grain size from 150 to 5 microns. As the temperature decreases, the yield strength and elongation increase. The effect of deformation rate on the mechanical properties is an increase in the ultimate strength and yield strength, which is most noticeable at high rates of 10–2 ÷ 103 s–1. The features of HEAs deformation behavior in the mono- and poly-crystalline states are noted. The complex of high operational properties of HEAs makes it possible to use them in various industries. There are good prospects of using energy treatment to modify the surface layers and further improve HEAs properties.

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Interstitials in f.c.c. High Entropy Alloys

Metals ◽

10.3390/met10050695 ◽

2020 ◽

Vol 10 (5) ◽

pp. 695 ◽

Cited By ~ 6

Author(s):

Ian Baker

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Yield Strength ◽

Room Temperature ◽

Sharp Decrease ◽

Slight Reduction ◽

Strength Increase ◽

High Entropy Alloys ◽

High Entropy ◽

Carbon Doped

The effects of interstitials on the mechanical properties of single-phase f.c.c. high entropy alloys (HEAs) have been assessed based on a review of the literature. It is found that in nearly all studies, carbon increases the yield strength, in some cases by more than in traditional alloys. This suggests that carbon can be an excellent way to strengthen HEAs. This strength increase is related to the lattice expansion from the carbon. The effects on other mechanical behavior is mixed. Most studies show a slight reduction in ductility due to carbon, but a few show increases in ductility accompanying the yield strength increase. Similarly, some studies show little or modest increases in work-hardening rate (WHR) due to carbon, whereas a few show a substantial increase. These latter effects are due to changes in deformation mode. For both undoped and carbon doped CoCrFeMnNi, the room temperature ductility decreases slightly with decreasing grain size until ~2–5 µm, below which the ductility appears to decrease rapidly. The room temperature WHR also appears to decrease with decreasing grain size in both undoped and carbon-doped CoCrFeMnNi and in nitrogen-doped medium entropy alloy NiCoCr, and, at least for the undoped HEA, shows a sharp decrease at grain sizes <2 µm. Interestingly, carbon has been shown to almost double the Hall–Petch strengthening in CoCrFeMnNi, suggesting the segregation of carbon to the grain boundaries. There have been few studies on the effects of other interstitials such as boron, nitrogen and hydrogen. It is clear that more research is needed on interstitials both to understand their effects on mechanical properties and to optimize their use.

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Effect of Heat Treatment on the Phase Composition, Microstructure and Mechanical Properties of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 High-Entropy Alloys

Metals ◽

10.3390/met8110974 ◽

2018 ◽

Vol 8 (11) ◽

pp. 974 ◽

Cited By ~ 1

Author(s):

Lijia Chen ◽

Kirsten Bobzin ◽

Zheng Zhou ◽

Lidong Zhao ◽

Mehmet Öte ◽

...

Keyword(s):

Mechanical Properties ◽

Phase Transition ◽

Heat Treatment ◽

Phase Composition ◽

Elevated Temperatures ◽

Intermetallic Phase ◽

Phase Changes ◽

High Entropy Alloys ◽

High Entropy ◽

Heat Treated

High-entropy alloys exhibit some interesting mechanical properties including an excellent resistance against softening at elevated temperatures. This gives high-entropy alloys (HEAs) great potential as new structural materials for high-temperature applications. In a previous study of the authors, oxidation behavior of Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys at T = 800 °C, 900 °C and 1000 °C was investigated. Si-alloying was found to increase the oxidation resistance by promoting the formation of a continuous Al2O3 layer, avoiding the formation of AlN at T = 800 °C. Obvious phase changes were identified in the surface areas of both alloys after the oxidation experiments. However, the effects of heat treatment and Si-alloying on the phase transition in the bulk were not investigated yet. In this study, Al0.6CrFeCoNi and Al0.6CrFeCoNiSi0.3 high-entropy alloys were heat-treated at T = 800 °C and T = 1000 °C to investigate the effect of heat treatment on microstructure, phase composition and mechanical properties of both alloys. The results show that alloying Al0.6CrFeCoNi with Si caused a phase transition from dual phases consisting of BCC and FCC to a single BCC phase in an as-cast condition. Furthermore, increased hardness for as-cast and heat-treated samples compared with the Al0.6CrFeCoNi alloy was observed. In addition, the heat treatment facilitated the phase transition and the precipitation of the intermetallic phase, which resulted in the change of the mechanical properties of the alloys.

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Microstructural Characteristics and Mechanical Behaviors of AlCoCrFeNi High-Entropy Alloys at Ambient and Cryogenic Temperatures

Materials Science Forum ◽

10.4028/www.scientific.net/msf.688.419 ◽

2011 ◽

Vol 688 ◽

pp. 419-425 ◽

Cited By ~ 60

Author(s):

Jun Wei Qiao ◽

S.G. Ma ◽

E.W. Huang ◽

C.P. Chuang ◽

P.K. Liaw ◽

...

Keyword(s):

Mechanical Properties ◽

Ambient Temperature ◽

Phase Formation ◽

Single Phase ◽

Size Difference ◽

High Entropy Alloys ◽

Cryogenic Temperatures ◽

Mechanical Behaviors ◽

Microstructural Characteristics ◽

High Entropy

The phase-formation rule of high-entropy alloys (HEAs) with different microstructures is discussed, based on the atom-size difference in multicomponent alloys. For the single-phase HEA with the composition of AlCoCrFeNi, the yielding strengths and fracture strengths at cryogenic temperatures increase distinguishingly, compared to the corresponding mechanical properties at ambient temperature. However, the plasticity at 298 and 77 K changes very gently, while the fracture modes are intergranular and transgranular, respectively.

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