Microstructures and compressive properties of AlxCoCrFeNi high entropy alloys prepared by arc melting and directional solidification

Abstract The AlxCoCrFeNi (molar radio, x=0.6 and 1.2) high entropy alloys (HEAs) were prepared by arc melting and directional solidification at the withdrawal rate of 150 μm/s. All microstructures were characterized by x-ray diffraction, optical microscopy and scanning electron microscopy with an energy-dispersive spectrometer. Strong similarities in phase constituent were observed between the as-cast samples and directionally solidified samples. The Al0.6CoCrFeNi HEA and Al1.2CoCrFeNi HEA fabricated by two different techniques respectively consisted of Cr-Fe-Co enriched FCC phase + Al-Ni enriched BCC phase and Al-Ni enriched B2 phase + Cr-Fe-Co enriched A2 phase. It was micromorphology found that directional solidification could not only make the microstructures arranged regularly but also coarsen the grains. This has been attributed to the preferred grain orientation and lower cooling rate during directional solidification process. Compression testing showed that the compressive ductility of directionally solidified samples decreased obviously. The ultimate compressive strength of Al0.6CoCrFeNi HEA increased from 1 675 MPa to 1 903 MPa, but the strength of Al1.2CoCrFeNi HEA decreased from 2 183 MPa to 1 463 MPa. The difference in strength has been suggested to be the result of micropores in the matrix.

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Microstructure and Microsegregation in Directionally Solidified FeCoNiCrAl High Entropy Alloy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.189-193.3840 ◽

2011 ◽

Vol 189-193 ◽

pp. 3840-3843 ◽

Cited By ~ 5

Author(s):

Hong Bao Cui ◽

Hai Yan Wang ◽

Jin Yong Wang ◽

Heng Zhi Fu

Keyword(s):

Directional Solidification ◽

Electron Microprobe ◽

Solidification Rate ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

Interface Morphology ◽

Directionally Solidified ◽

High Entropy ◽

Interdendritic Segregation ◽

Cast Condition

Directional solidification (DS) of FeCoNiCrAl high entropy alloy is carried out to investigate the microstructures and microsegregation under controlled solidification conditions. With an increasing solidification rate, the interface morphology grows in a planar, cellular and dendritic manner. The microstructures of the dendritic and interdendritic segregation areas are found to be spherical precipitates and basket-weave structures, respectively. With the help of an electron microprobe, microsegregation is determined in directionally solidified FeCoNiCrAl high entropy alloys. In contrast to the as-cast condition, directional solidification can refine microstructures of FeCoNiCrAl high entropy alloy dramatically and reduce microsegregation effectively.

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

Journal of Physics and Electronics ◽

10.15421/331806 ◽

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.

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The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133114 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1696-1697

Author(s):

H.J. Zuo ◽

M.W. Price ◽

R.D. Griffin ◽

R.A. Andrews ◽

G.M. Janowski

Keyword(s):

Directional Solidification ◽

Space Shuttle ◽

Solidification Process ◽

Space Experiment ◽

Infrared Detection ◽

Directionally Solidified ◽

Crystallographic Defects ◽

Semiconducting Alloys ◽

Uniform Composition ◽

Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

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Microstructure and Mechanical Properties of VTaTiMoAlx Refractory High Entropy Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.898.638 ◽

2017 ◽

Vol 898 ◽

pp. 638-642 ◽

Cited By ~ 7

Author(s):

Dong Xu Qiao ◽

Hui Jiang ◽

Xiao Xue Chang ◽

Yi Ping Lu ◽

Ting Ju Li

Keyword(s):

Mechanical Properties ◽

Vacuum Arc ◽

High Entropy Alloys ◽

X Ray Diffraction ◽

Dendrite Structure ◽

X Ray ◽

High Entropy ◽

Arc Melting ◽

Vacuum Arc Melting ◽

Microstructure And Mechanical Properties

A series of refractory high-entropy alloys VTaTiMoAlx with x=0,0.2,0.6,1.0 were designed and produced by vacuum arc melting. The effect of added Al elements on the microstructure and mechanical properties of refractory high-entropy alloys were investigated. The X-ray diffraction results showed that all the high-entropy alloys consist of simple BCC solid solution. SEM indicated that the microstructure of VTaTiMoAlx changes from equiaxial dendritic-like structure to typical dendrite structure with the addition of Al element. The composition of different regions in the alloys are obtained by energy dispersive spectroscopy and shows that Ta, Mo elements are enriched in the dendrite areas, and Al, Ti, V are enriched in inter-dendrite areas. The yield strength and compress strain reach maximum (σ0.2=1221MPa, ε=9.91%) at x=0, and decrease with the addition of Al element at room temperature. Vickers hardness of the alloys improves as the Al addition.

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

Materials ◽

10.3390/ma12244222 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4222 ◽

Cited By ~ 2

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.

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Microstructure and mechanical properties of RexNbMoTaW high-entropy alloys prepared by arc melting using metal powders

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2020.154301 ◽

2020 ◽

Vol 827 ◽

pp. 154301 ◽

Cited By ~ 6

Author(s):

Jian Zhang ◽

Yeyuan Hu ◽

Qinqin Wei ◽

Yuan Xiao ◽

Pingan Chen ◽

...

Keyword(s):

Mechanical Properties ◽

High Entropy Alloys ◽

Metal Powders ◽

High Entropy ◽

Arc Melting ◽

Microstructure And Mechanical Properties

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Mechanical Behavior of Novel Suction Cast Ti-Cu-Fe-Co-Ni High Entropy Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.790-791.503 ◽

2014 ◽

Vol 790-791 ◽

pp. 503-508 ◽

Cited By ~ 22

Author(s):

Sumanta Samal ◽

Sutanuka Mohanty ◽

Ajit Kumar Misra ◽

Krishanu Biswas ◽

B. Govind

Keyword(s):

Mechanical Properties ◽

Vacuum Arc ◽

High Entropy Alloys ◽

The Novel ◽

Electron Microscopic ◽

High Entropy ◽

Alloy Chemistry ◽

Arc Melting ◽

Vacuum Arc Melting ◽

Ductile Mode

The present investigation reports mechanical properties of novel multicomponent TixCuyFe20Co20Ni20 high entropy alloys (HEAs) with different alloy chemistry (x/y = 1/3, 3/7, 3/5, 9/11, 1, 11/9 and 3/2). The alloy cylinders were prepared by vacuum arc melting-cum-suction casting route. The detailed electron microscopic observations reveal the presence of three different solid solution phases; FCC (a1) phase, FCC (a2) phase and BCC (b) phase for all the investigated alloys, whereas ultrafine eutectic between FCC (a1) phase, and Ti2 (Co, Ni) - type Laves phase has been observed for the HEAs with x/y = 9/11, 1, 11/9 and 3/2. Room temperature compression test of the suction cast cylinders with aspect ratio of 2/1 has been conducted to obtain mechanical properties of the HEAs. The optimum combination of strength (~ 1.88 GPa) and plasticity (~ 21 %) is obtained for x/y = 9/11; indicating simultaneous improvement of strength as well as plasticity of the novel HEAs. Fractographic analysis of the fractured surfaces reveals mixed mode of fracture for x/y = 1/3, 3/7 and 3/5, ductile mode for x/y = 9/11 and 1, whereas brittle mode of fracture for x/y = 11/9 and 3/2.

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The Effect of Boron on the Microstructure and Properties of Refractory Metal Intermetallic Composites (RM(Nb)ICs) Based on Nb-24Ti-xSi (x = 16, 17 or 18 at.%) with Additions of Al, Cr or Mo

Materials ◽

10.3390/ma14206101 ◽

2021 ◽

Vol 14 (20) ◽

pp. 6101

Author(s):

Tophan Thandorn ◽

Panos Tsakiropoulos

Keyword(s):

Refractory Metal ◽

Design Methodology ◽

Room Temperature ◽

High Entropy Alloys ◽

Scale Spallation ◽

High Entropy ◽

Specific Strength ◽

Arc Melting ◽

High Temperature Materials ◽

Heat Treated

This paper is about metallic ultra-high temperature materials, in particular, refractory metal intermetallic composites based on Nb, i.e., RM(Nb)ICs, with the addition of boron, which are compared with refractory metal high entropy alloys (RHEAs) or refractory metal complex concentrated alloys (RCCAs). We studied the effect of B addition on the density, macrosegregation, microstructure, hardness and oxidation of four RM(Nb)IC alloys, namely the alloys TT2, TT3, TT4 and TT8 with nominal compositions (at.%) Nb-24Ti-16Si-5Cr-7B, Nb-24Ti-16Si-5Al-7B, Nb-24Ti-18Si-5Al-5Cr-8B and Nb-24Ti-17Si-3.5Al-5Cr-6B-2Mo, respectively. The alloys made it possible to compare the effect of B addition on density, hardness or oxidation with that of Ge or Sn addition. The alloys were made using arc melting and their microstructures were characterised in the as cast and heat-treated conditions. The B macrosegregation was highest in TT8. The macrosegregation of Si or Ti increased with the addition of B and was lowest in TT8. The alloy TT8 had the lowest density of 6.41 g/cm3 and the highest specific strength at room temperature, which was also higher than that of RCCAs and RHEAs. The Nbss and T2 silicide were stable in the alloys TT2 and TT3, whereas in TT4 and TT8 the stable phases were the Nbss and the T2 and D88 silicides. Compared with the Ge or Sn addition in the same reference alloy, the B and Ge addition was the least and most effective at 800 °C (i.e., in the pest regime), when no other RM was present in the alloy. Like Ge or Sn, the B addition in TT2, TT3 and TT4 did not suppress scale spallation at 1200 °C. Only the alloy TT8 did not pest and its scales did not spall off at 800 and 1200 °C. The macrosegregation of Si and Ti, the chemical composition of Nbss and T2, the microhardness of Nbss and the hardness of alloys, and the oxidation of the alloys at 800 and 1200 °C were also viewed from the perspective of the alloy design methodology NICE and relationships with the alloy or phase parameters VEC, δ and Δχ. The trends of these parameters and the location of alloys and phases in parameter maps were found to be in agreement with NICE.

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