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

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.

Download Full-text

Microstructure and Mechanical Properties of FeNiCrCuAl High Entropy Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1036.101 ◽

2014 ◽

Vol 1036 ◽

pp. 101-105

Author(s):

Gheorghe Buluc ◽

Iulia Florea ◽

Oana Bălţătescu ◽

Costel Roman ◽

Ioan Carcea

Keyword(s):

Mechanical Properties ◽

Solid Solution ◽

High Hardness ◽

High Strength ◽

High Entropy Alloys ◽

Engineering Applications ◽

High Entropy ◽

Good Thermal Stability ◽

Microstructure And Mechanical Properties ◽

Wide Range

This paper presents the microstructure and the mechanical properties of FeNiCrCuAl high entropy alloys. The microstructure and mechanical properties of the annealed FeNiCrCuAl high entropy alloys were investigated using scanning electron microscopy, and X-ray diffraction. High entropy alloys have been known as a new type of materials and have been defined as having five or more principal elements, each one having a concentration between 5 and 35 at.%. Previous researches show that HEAs can be processed to form simple solid solution structures instead of intermetallics and other complicated compounds. This phenomenon is commonly attributed to the high configurational entropy in the solid solution state of HEAs. Furthermore, HEAs have also exhibited interesting properties such as high hardness and high strength, good thermal stability outstanding wear and oxidation resistance which offer great potential for engineering applications. The HEA systems explored in the past decade show that metallic elements are the most commonly used, e.g. Al, Cr, Fe, Co, Ni, Cu,Ti, etc. A wide range of HEAs exhibit high hardness, high strength, distinctive electrical and magnetic properties, high-temperature softening resistance, as well as favorable combination of compression strength and ductility. This combination of properties and the particular structures of HEAs are attractive for a number of potential engineering applications.

Download Full-text

Preparing bulk ultrafine-microstructure high-entropy alloys via direct solidification

Nanoscale ◽

10.1039/c7nr07281c ◽

2018 ◽

Vol 10 (4) ◽

pp. 1912-1919 ◽

Cited By ~ 28

Author(s):

Yiping Lu ◽

Xiaoxia Gao ◽

Yong Dong ◽

Tongmin Wang ◽

Hai-Lin Chen ◽

...

Keyword(s):

Mechanical Properties ◽

High Strength ◽

High Entropy Alloys ◽

High Entropy ◽

The Past

In the past three decades, nanostructured (NS) and ultrafine-microstructure (UFM) materials have received extensive attention due to their excellent mechanical properties such as high strength.

Download Full-text

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.

Download Full-text

Properties and Preparation of High Entropy Alloys

MATEC Web of Conferences ◽

10.1051/matecconf/201814203003 ◽

2018 ◽

Vol 142 ◽

pp. 03003 ◽

Cited By ~ 1

Author(s):

Xiang Yin ◽

Shuqiong Xu

Keyword(s):

Mechanical Properties ◽

Lattice Distortion ◽

Chemical Properties ◽

High Strength ◽

High Entropy Alloys ◽

Cocktail Party ◽

High Entropy ◽

Comprehensive Properties ◽

Cocktail Party Effect ◽

And Chemical Properties

As a consequence of multi-components, the high entropy alloys embodied serious cocktail party effect and lattice distortion. So high entropy alloys have high strength and hardness possess many comprehensive properties such as thermostability and corrosion resistance. Because of excellent mechanical properties and chemical properties, high entropy alloys have immeasurable potential of development. This paper mainly introduces the properties, preparations and applications of high entropy alloys, and finally summarizes them.

Download Full-text

DETERMINATION OF THE CAUSES OF DESTRUCTION OF HIGH-STRENGTH FASTENING ELEMENTS

Problems of Strength and Plasticity ◽

10.32326/1814-9146-2021-83-2-207-219 ◽

2021 ◽

Vol 83 (2) ◽

pp. 207-219

Author(s):

O.B. Berdnik ◽

I.N. Tsareva ◽

L.A. Krivina ◽

S.V. Kirikov ◽

Yu.P. Tarasenko ◽

...

Keyword(s):

Mechanical Properties ◽

Phase Composition ◽

Physical And Mechanical Properties ◽

High Strength ◽

Mechanical Tests ◽

Modern Technology ◽

Regulatory Requirements ◽

Two Phase ◽

Average Value ◽

Elastic And Plastic Deformations

Intensively operated modern technology requires the use of high-strength fasteners. The article presents the results of studies of the structure and physical and mechanical properties of the material of fastening elements (threaded hardware) in order to determine the causes of their destruction during operation. The fractographic analysis of fractures of fractured bolts revealed pronounced centers of crack initiation with traces of delayed brittle fracture, which is typical for high-strength hardware that are under high load for a long time, close to the yield point. Mechanical tests of the studied fastening elements showed increased values of ultimate strength. The performed relaxation tests of the material of broken bolts also revealed an increased value of the microplasticity limit, which is responsible for the onset of plastic deformation processes in microvolumes of the material, and for the material of whole hardware, the value of the limit is included in the permissible interval. At the same time, the average hardness of the material of all products meets the regulatory requirements. The maximum spread of hardness 70 HB is fixed on the destroyed bolt. Using the experimental values of microhardness, theoretical estimates of the coefficient of plasticity, which characterize the ability of a material to perceive elastic and plastic deformations, were carried out. To ensure a sufficient level of ductility of a long-term working metal material, the ductility coefficient must be at least 0.8. The average value of the hardness of the material of the fastening elements satisfies this criterion for assessing ductility. According to the results of a step-by-step analysis of the microstructure of the samples, the inhomogeneity of the distribution of the carbide phase over the cross-section of the bolts was established. The two-phase composition (a-Fe + Fe3C) of steel was established by X-ray structural analysis, which confirms the results of microstructural studies. It should be noted that the phase composition of all studied samples is identical. Based on the results of the studies carried out, it was found that the destruction occurred due to the reduced strength and increased fragility of the material due to the presence of microdefects. The material of the whole bolts in terms of structure and mechanical properties comply with regulatory requirements.

Download Full-text

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.

Download Full-text

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.

Download Full-text

Mechanical properties of the CoCrFeNiMnV x high entropy alloys in temperature range 4.2–300 K

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2016.12.154 ◽

2017 ◽

Vol 698 ◽

pp. 501-509 ◽

Cited By ~ 24

Author(s):

Е.D. Tabachnikova ◽

А.V. Podolskiy ◽

M.O. Laktionova ◽

N.A. Bereznaia ◽

M.A. Tikhonovsky ◽

...

Keyword(s):

Mechanical Properties ◽

High Entropy Alloys ◽

High Entropy ◽

Temperature Range

Download Full-text

High-strength wire + arc additive manufactured steel

International Journal of Materials Research (formerly Zeitschrift fuer Metallkunde) ◽

10.1515/ijmr-2020-1110408 ◽

2020 ◽

Vol 111 (4) ◽

pp. 325-331

Author(s):

Chun Guo ◽

Maoxue Liu ◽

Ruizhang Hu ◽

Tuoyu Yang ◽

Baoli Wei ◽

...

Keyword(s):

Crystal Structure ◽

Mechanical Properties ◽

Tensile Strength ◽

Phase Composition ◽

Yield Strength ◽

Charpy Impact ◽

High Strength ◽

Granular Bainite ◽

Microhardness Distribution ◽

Wire Arc Additive Manufacturing

Abstract High-strength 690-MPa steel was prepared using a wire + arc additive manufacturing (WAAM) technology. The phase composition, microstructure, and crystal structure of highstrength 690-MPa steel samples were analysed, and the results show that a sample prepared using WAAM technology achieves a good formation quality. The metallographic structure was mainly acicular ferrite, massive ferrite, and granular bainite. The microhardness distribution of the vertical and horizontal sections of the samples is uniform. Excellent mechanical properties of the specimen were shown, including a horizontal yield strength of 536 MPa, a tensile strength of 760 MPa, an elongation of 23.5%, a Charpy impact value of 70 J at -508C, a vertical yield strength of 486 MPa, a tensile strength of 758 MPa, an elongation of 21.5%, and a Charpy impact value of 51 J at -508C.

Download Full-text