scholarly journals Microstructural Evolution from Dendrites to Core-Shell Equiaxed Grain Morphology for CoCrFeNiVx High-Entropy Alloys in Metallic Casting Mold

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1172 ◽  
Author(s):  
Leigang Cao ◽  
Lin Zhu ◽  
Hongde Shi ◽  
Zerui Wang ◽  
Yue Yang ◽  
...  
Keyword(s):  
Grain Morphology ◽  
Core Region ◽  
Core Shell ◽  
High Entropy Alloys ◽  
Σ Phase ◽  
High Entropy ◽  
The Core ◽  
Interdendrite Region ◽  
Fcc Phase ◽  
Equiaxed Grain

The CoCrFeNiVx (x = 0, 0.25, 0.5, 0.7, 0.8, 0.9, and 1.0) high-entropy alloys (HEAs) were fabricated by the copper mold casting process. The microstructure, phase constitution, and mechanical properties were investigated by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy analyses and compressive testing. It revealed that, when x ≤ 0.25, the alloys solidified into a single fcc phase. When 0.5 ≤ x ≤ 0.8, the alloys solidified into a dendritic structure of the fcc phase with the formation of the σ phase in the interdendrite region. Interestingly, when x exceeded 0.9, the alloys presented a typical core-shell equiaxed grain morphology. The core region consisting of a mixture of fcc + σ phases was surrounded by the shell of the single σ phase and the interdendrite region solidified into the single fcc phase. The dual-phase “eutectiod” structure in the core region of the equiaxed grain might be formed from the decomposition of the unidentified metastable phase. As the V fraction increased, the compressive yield strength of the CoCrFeNiVx alloys gradually increased from 164 MPa (x = 0) to 458 MPa (x = 0.8), and then sharply increased to 722 MPa (x = 0.9) and 1493 MPa (x = 1.0).

Temperature Dependent Yield Strength, Strain Hardening and Failure of the CoCrFeNiMnVx High Entropy Alloys

2017 ◽  
Vol 891 ◽  
pp. 438-443
Author(s):  
Aleksey V. Podolskiy ◽  
Elena D. Tabachnikova ◽  
Marina O. Laktionova ◽  
Natalia A. Bereznaia ◽  
Mikhail A. Tikhonovsky ◽  
...  
Keyword(s):  
Yield Strength ◽  
Strain Hardening ◽  
High Entropy Alloys ◽  
Temperature Dependent ◽  
Σ Phase ◽  
High Entropy ◽  
Temperature Dependences ◽  
Fcc Phase ◽  
Different Content ◽  
Main Deformation

Several structural states of the CoCrFeNiMnVx (x=0, 0.25, 0.5, 0.75) high entropy alloys with different content of the intermetallic σ phase are studied in uniaxial compression in temperature range 4.2-300 K. Peculiarities of strain hardening stages and temperature dependences of the yield strength are registered and analyzed considering dislocation sliding as main deformation mechanism in matrix fcc phase. Influence of σ phase particles, deformation twins and stacking faults on the deformation behavior of the CoCrFeNiMnVx alloy is discussed.

scholarly journals Effects of the Replacement of Co with Ni on the Microstructure, Mechanical Properties, and Age Hardening of AlCo1−xCrFeNi1+x High-Entropy Alloys

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2665
Author(s):  
Che-Fu Lee ◽  
Tao-Tsung Shun
Keyword(s):  
Mechanical Properties ◽  
Fracture Strain ◽  
Dendritic Structure ◽  
Age Hardening ◽  
Molar Ratio ◽  
High Entropy Alloys ◽  
Σ Phase ◽  
High Entropy ◽  
Fcc Phase ◽  
Bcc Phase

In this study, effects of the replacement of Co with Ni on the microstructure, mechanical properties, and age hardening of high-entropy alloys of AlCo1−xCrFeNi1+x (x = molar ratio; x = 0, 0.5, 1, denoted as X0, X0.5, and X1, respectively) were investigated. These three alloys exhibited a dendritic structure comprising an ordered BCC matrix, a BCC phase, and an FCC or an ordered FCC phase. From X0 to X1 alloys, the yield stress and compressive stress decreased from 1202 and 1790 MPa to 693 and 1537 MPa, respectively. However, fracture strain increased from 0.15 to 0.42. Peak age hardening at 600 °C for the X0 alloy was due to the precipitation of the (Cr,Fe)-rich σ phase. Peak age hardening for the X0.5 and X1 alloys was observed at 500 °C because of the precipitation of the σ phase and BCC phase, respectively.

scholarly journals The AC Soft Magnetic Properties of FeCoNixCuAl (1.0 ≤ x ≤ 1.75) High-Entropy Alloys

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4222 ◽  
Author(s):  
Zhongyuan Wu ◽  
Chenxu Wang ◽  
Yin Zhang ◽  
Xiaomeng Feng ◽  
Yong Gu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Soft Magnetic Materials ◽  
Magnetic Flux Density ◽  
High Entropy Alloys ◽  
Soft Magnetic Properties ◽  
Phase Content ◽  
Soft Magnetic ◽  
High Entropy ◽  
Two Phases ◽  
Fcc Phase

High-entropy alloys (HEAs) with soft magnetic properties are one of the new candidate soft magnetic materials which are usually used under an alternating current (AC) magnetic field. In this work, the AC soft magnetic properties are investigated for FeCoNixCuAl (1.0 ≤ x ≤ 1.75) HEAs. The X-ray diffraction (XRD) and scanning electron microscope (SEM) show that the alloy consists of two phases, namely a face-centred cubic (FCC) phase and a body-centred cubic (BCC) phase. With increasing Ni content, the FCC phase content increased. Further research shows that the AC soft magnetic properties of these alloys are closely related to their phase constitution. Increasing the FCC phase content contributes to a decrease in the values of AC remanence (AC Br), AC coercivity (AC Hc) and AC total loss (Ps), while it is harmful to the AC maximum magnetic flux density (AC Bm). Ps can be divided into two parts: AC hysteresis loss (Ph) and eddy current loss (Pe). With increasing frequency f, the ratio of Ph/Ps decreases for all samples. When f ≤ 150 Hz, Ph/Ps > 70%, which means that Ph mainly contributes to Ps. When f ≥ 800 Hz, Ph/Ps < 40% (except for the x = 1.0 sample), which means that Pe mainly contributes to Ps. At the same frequency, the ratio of Ph/Ps decreases gradually with increasing FCC phase content. The values of Pe and Ph are mainly related to the electrical resistivity (ρ) and the AC Hc, respectively. This provides a direction to reduce Ps.

scholarly journals Selective Cation Exchange in the Core Region of Cu2–xSe/Cu2–xS Core/Shell Nanocrystals

2015 ◽  
Vol 137 (38) ◽  
pp. 12195-12198 ◽  
Author(s):  
Karol Miszta ◽  
Graziella Gariano ◽  
Rosaria Brescia ◽  
Sergio Marras ◽  
Francesco De Donato ◽  
...  
Keyword(s):  
Cation Exchange ◽  
Core Region ◽  
Core Shell ◽  
The Core

scholarly journals The effect of cooling rate on the magnetic properties of Cu-Fe-Ni multicomponent alloys with Al and Si additions

2018 ◽  
Vol 26 (1) ◽  
pp. 39-44
Author(s):  
O. I. Kushnerov ◽  
V. F. Bashev
Keyword(s):  
Magnetic Properties ◽  
Cooling Rate ◽  
Alloy System ◽  
Enthalpy Of Mixing ◽  
Soft Magnetic Materials ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Leading Role ◽  
The Difference ◽  
Fcc Phase

The paper explores the structure and magnetic properties of multicomponent high-entropy Al-Cu-Fe-Ni-Si alloys in as-cast and splat-quenched state. This alloy system is characterized by the absence of expensive components, such as Co, V, Mo, Cr, usually used for the production of high-entropy alloys while its characteristics are not inferior to those of more expensive alloys. Components of the studied high-entropy alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. The alloy films were fabricated by a known technique of splat-quenching. A cooling rate estimated by film thickness was ~ 106 K/s. Experimental results reveal that the studied alloys except the Al0.5CuFeNi one are multiphase, with the structure consisting of disordered BCC and FCC solid solutions. The Al0.5CuFeNi alloy has only FCC phase. The leading role in determining the type of solid solution formed in the studied high-entropy films obviously plays an element with the highest melting point. All of the investigated multicomponent films are soft magnetic materials as indicated by low values of coercivity, while most of the as-cast alloys are hard-magnetic.

scholarly journals Effect of Molybdenum Additives on Corrosion Behavior of (CoCrFeNi)100−xMox High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (12) ◽  
pp. 908 ◽  
Author(s):  
Wenrui Wang ◽  
Jieqian Wang ◽  
Honggang Yi ◽  
Wu Qi ◽  
Qing Peng
Keyword(s):  
Corrosion Behavior ◽  
Compressive Strain ◽  
Compressive Yield Strength ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
Σ Phase ◽  
High Entropy ◽  
Passivation Film ◽  
Face Centered ◽  
Mo Content

The present work investigates the influence of micro-alloyed Mo on the corrosion behavior of (CoCrFeNi)100−xMox high-entropy alloys. All of the (CoCrFeNi)100−xMox alloys exhibit a single face-centered cubic (FCC) solid solution. However, the (CoCrFeNi)97Mo3 alloy exhibits an ordered sigma (σ) phase enriched in Cr and Mo. With the increase of x (the Mo content) from 1 to 3, the hardness of the (CoCrFeNi)100−xMox alloys increases from 124.8 to 133.6 Vickers hardness (HV), and the compressive yield strength increases from 113.6 MPa to 141.1 MPa, without fracture under about a 60% compressive strain. The potentiodynamic polarization curve in a 3.5% NaCl solution indicates that the addition of Mo has a beneficial effect on the corrosion resistance to some certain extent, opposed to the σ phase. Furthermore, the alloys tend to form a passivation film in the 0.5 M H2SO4 solution in order to inhibit the progress of the corrosion reaction as the Mo content increases.

scholarly journals Magnetic Properties and Microstructure of FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (11) ◽  
pp. 872 ◽  
Author(s):  
Zhong Li ◽  
Chenxu Wang ◽  
Linye Yu ◽  
Yong Gu ◽  
Minxiang Pan ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Tc ◽  
Soft Magnets ◽  
High Entropy ◽  
Face Centered ◽  
Fcc Phase ◽  
Bcc Phase ◽  
Curie Temperatures

The present work exhibits the effects of Sn addition on the magnetic properties and microstructure of FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) high-entropy alloys (HEAs). The results show all the samples consist of a mixed structure of face-centered-cubic (FCC) phase and body-centered-cubic (BCC) phase. The addition of Sn promotes the formation of BCC phase, and it also affects the shape of Cu-rich nano-precipitates in BCC matrix. It also shows that the Curie temperatures (Tc) of the FCC phase and the saturation magnetization (Ms) of the FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) HEAs increase greatly while the remanence (Br) decreases after the addition of Sn into FeCoNi(CuAl)0.8 HEA. The thermomagnetic curves indicate that the phases of the FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) HEAs will transform from FCC with low Tc to BCC phase with high Tc at temperature of 600–700 K. This work provides a new idea for FeCoNi(CuAl)0.8Snx (0 ≤ x ≤ 0.10) HEAs for their potential application as soft magnets to be used at high temperatures.

Effect of the Annealing Treatment on the Microstructure, Microhardness and Corrosion Behaviour of Al0.3CrFe1.5MnNi0.5 High-Entropy Alloys

2013 ◽  
Vol 748 ◽  
pp. 79-85 ◽  
Author(s):  
L.C. Tsao ◽  
C.S. Chen ◽  
Kuo Huan Fan ◽  
Yen Teng Huang
Keyword(s):  
Corrosion Behaviour ◽  
Dendritic Structure ◽  
Annealing Treatment ◽  
Age Hardening ◽  
High Entropy Alloy ◽  
Second Phase ◽  
High Entropy Alloys ◽  
High Entropy ◽  
Fcc Phase ◽  
Bcc Phase

In this study, an Al0.3CrFe1.5MnNi0.5high entropy alloy was synthesized by arc-melting in Ar. The as-cast alloy ingot was heat treated for 8 h at 650-750°C and then cooled in furnace to investigate the effects of age treatment on the microstructure, hardness and corrosion behaviour. The microstructure of as-cast sample has a typical rich-Cr BCC structure of dendrites, rich-Ni FCC interdendrite phases and a small fraction of cross-like rich-Ni FCC phase within the majority dendritic structure. During annealing treatment at 650°C, the cross-like FCC phase (β-FCC) gradually decreased, dendritic rich-Cr BCC phase transfers to Cr5Fe6Mn8phase, and the AlNi phase precipitated within the matrix dendrites. The interdendritic β1-FCC phases gradually decomposed and transfers to second-phase (β2FCC), and the AlNi precipitated phase coarsen during annealing at 750°C. In addition, Cr5Fe6Mn8phase gradually transfers to rich-Cr BCC phase during slow-cooling process. These precipitation phases in the grain matrix are the main age hardening mechanism. The potentiodynamic polarization of the Al0.3CrFe1.5MnNi0.5high entropy alloys, obtained in 3.5% NaCl solutions, clearly revealed that the corrosion resistance increases and the passive region decreases as annealing temperature increasing.

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