Another eutectic point of Co–Cr–Fe–Ni-M (Hf, Ta, Nb) high-entropy system determined using a simple mixture method correlated with mixing enthalpy

To study the effect of alloy composition on phase selection in the CoCrCu0.1FeMoNi high-entropy alloy (HEA), Mo was partially replaced by Co, Cr, Fe, and Ni. The microstructures and phase selection behaviors of the CoCrCu0.1FeMoNi HEA system were investigated. Dendritic, inter-dendritic, and eutectic microstructures were observed in the as-solidified HEAs. A simple face centered cubic (FCC) single-phase solid solution was obtained when the molar ratio of Fe, Co, and Ni was increased to 1.7 at the expense of Mo, indicating that Fe, Co, and Ni stabilized the FCC structure. The FCC structure was favored at the atomic radius ratio δ ≤ 2.8, valence electron concentration (VEC) ≥ 8.27, mixing entropy ΔS ≤ 13.037, local lattice distortion parameter α2 ≤ 0.0051, and ΔS/δ2 > 1.7. Mixed FCC + body centered cubic (BCC) structures occurred for 4.1 ≤ δ ≤ 4.3 and 7.71 ≤ VEC ≤ 7.86; FCC or/and BCC + intermetallic (IM) mixtures were favored at 2.8 ≤ δ ≤ 4.1 or δ > 4.3 and 7.39 < VEC ≤ 8.27. The IM phase is favored at electronegativity differences greater than 0.133. However, ΔS, α2, and ΔS/δ2 were inefficient in identifying the (FCC or/and BCC + IM)/(FCC + BCC) transition. Moreover, the mixing enthalpy cannot predict phase structures in this system.

Download Full-text

Microstructural Evolution and Hardness of CoxCrCuFeNi High-Entropy Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.789.79 ◽

2014 ◽

Vol 789 ◽

pp. 79-83 ◽

Cited By ~ 2

Author(s):

Xing Yan Gao ◽

Ning Liu ◽

Yun Xue Jin ◽

Zhi Xuan Zhu

Keyword(s):

Supersaturated Solid Solution ◽

Xrd Analysis ◽

Mixing Enthalpy ◽

High Entropy Alloys ◽

Micro Hardness ◽

Hardness Testing ◽

Cooling Process ◽

High Entropy ◽

Interdendritic Phase ◽

Microstructure Characteristic

The effects of Co contents on the microstructure characteristic and phase structure of CoxCrCuFeNi high-entropy alloys were investigated by SEM, EDS and XRD. The microstructures consisted of dendrites and many nanoprecipitations in the interdendritic. Increase Co contents,the size of nanoprecipitated phase in the interdendritic firstly increased and then decreased slightly. According to XRD analysis, two simple FCC phases, dendrite phase and Cu-rich interdendritic phase were found. As a result of slow diffusion, supersaturated solid solution was formed during solidification and then nanophase was precipitated during the following cooling process. The results of EDS revealed that Fe、Co and Cr were rich in dendrites, while Cu was rich at the interdendritic. For element Ni, which was rich in dendrites when x≤1.0, but was almost the normal value in dendrites for x>1.0. The reason for segregation was related to the positive mixing enthalpy between elements. The contents of Co had little impact on the hardness of CoxCrCuFeNi high-entropy alloys according to micro-hardness testing.

Download Full-text

A new pseudo binary strategy to design eutectic high entropy alloys using mixing enthalpy and valence electron concentration

Materials & Design ◽

10.1016/j.matdes.2018.01.057 ◽

2018 ◽

Vol 143 ◽

pp. 49-55 ◽

Cited By ~ 36

Author(s):

Xi Jin ◽

Yang Zhou ◽

Lu Zhang ◽

Xingyu Du ◽

Bangsheng Li

Keyword(s):

Electron Concentration ◽

Valence Electron ◽

Mixing Enthalpy ◽

Valence Electron Concentration ◽

High Entropy Alloys ◽

High Entropy

Download Full-text

Microstructure and Mechanical Properties of Equiatomic CrMnCoNiCu High Entropy Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.909.39 ◽

2017 ◽

Vol 909 ◽

pp. 39-43 ◽

Cited By ~ 1

Author(s):

Seung Min Oh ◽

Sun Ig Hong

Keyword(s):

Mechanical Properties ◽

Cast Alloy ◽

True Strain ◽

Peak Height ◽

Mixing Enthalpy ◽

High Entropy Alloy ◽

Solid Solution Phase ◽

Rich Phase ◽

High Entropy ◽

Microstructure And Mechanical Properties

Microstructure and mechanical properties of equiatomic CrMnCoNiCu alloy in which Fe was substituted by Cu from Cantor alloy was studied. The separation of solid solution phase into two solid solutions (Cr-Co rich and Cu-rich phases) were observed in CrMnCoNiCu. The coarsening and widening of interdendritic Cu-rich phase after homogenization was observed and supported by the increase of XRD peak height from Cu-rich phase compared to that from Cr-Co rich phase after homogenization. The increase of the peak from Cu-rich phase can be attributed to the thermodynamic stability of Cu due to positive mixing enthalpy of adding Cu. The stress-strain curves of CrMnCoNiCu alloy exhibited the reasonably high strength and excellent deformability for the cast alloy. The yield stress of CrMnCoNiCu was observed to be 390MPa and it could be deformed without crack formation up to the true strain 0.85 to reach the flow stress as high as 662Mpa.

Download Full-text

Necessary Thermodynamics Factors to Obtain Simple Solid Solutions in High-Entropy Alloys from the Al-Ti-Co-Ni-Fe System

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0316 ◽

2017 ◽

Vol 62 (4) ◽

pp. 2141-2145 ◽

Cited By ~ 2

Author(s):

K. Górecki ◽

P. Bała ◽

T. Kozieł ◽

G. Cios

Keyword(s):

Crystal Structure ◽

Electron Concentration ◽

Valence Electron ◽

Intermetallic Phases ◽

Mixing Enthalpy ◽

Valence Electron Concentration ◽

High Entropy Alloys ◽

High Entropy ◽

Mixing Entropy ◽

Design And Synthesis

AbstractIn this paper findings regarding the design and synthesis of High-Entropy Alloys based on mixing enthalpy, mixing entropy,δparameter, Ω parameter and valence electron concentration are presented. Four alloys were synthesised with different predicted crystalline structures. Results of the microstructure and crystal structure studies are presented. It was shown that predicted structures as well as complex intermetallic phases exist in the material. The validity of valence electron concentration as well as additional parameters such as mixing enthalpy, mixing entropy and others necessary to obtain only the solid solution in High-Entropy Alloys were examined.

Download Full-text

On the Al–Al11Ce3 Eutectic Transformation in Aluminum–Cerium Binary Alloys

Materials ◽

10.3390/ma13204549 ◽

2020 ◽

Vol 13 (20) ◽

pp. 4549

Author(s):

Frank Czerwinski ◽

Babak Shalchi Amirkhiz

Keyword(s):

Binary Alloys ◽

Eutectic Point ◽

Eutectic Structure ◽

Eutectic Phase ◽

Atomic Scale ◽

Orientation Relationships ◽

High Entropy ◽

Eutectic Transformation

The L ↔ Al + Al11Ce3 technologically important eutectic transformation in Al–Ce binary alloys, containing from 5 to 20 wt.% Ce and ranging from hypo- to hypereutectic compositions, was examined along with the microstructure and properties of its solidified product. A combination of thermal analysis and metallography determined the coordinates of the eutectic point at 644.5 ± 0.6 °C and 10.6 wt.% Ce, clarifying the existing literature ambiguity. Despite the high entropy of melting of the Al11Ce3 phase, in hypoeutectic alloys the eutectic was dominated by the regular morphology of periodically arranged lamellae, typical for non-faceted systems. In the lamellar eutectic, however, the faceting of Al11Ce3 was identified at the atomic scale. In contrast, for hypereutectic compositions, the Al11Ce3 eutectic phase exhibited complex morphology, influenced by the proeutectic Al11Ce3 phase. The Al11Ce3 eutectic phase lost its coherency with Al; it was deduced that a partial coherency was present only at early stages of lamellae growth. The orientation relationships between the Al11Ce3 and Al in the eutectic structure, leading to partial coherency, were determined to be [0 0 1]Al ║ [1¯ 1 1]Al11Ce3 with (0 4 4¯)Al ║ (2¯ 0 0)Al11Ce3 and [0 1 1]Al ║ [3¯ 0 1]Al11Ce3 with (2¯ 0 0)Al ║ (0 6 0)Al11Ce3. The Al11Ce3 phase with a hardness of 350 HV and Al matrix having 35 HV in their eutectic arrangement formed in situ composite, with the former playing a role of reinforcement. However, the coarse and mostly incoherent Al11Ce3 eutectic phase provided limited strengthening and the Al–Ce alloy consisting of 100% eutectic reached at room temperature a yield stress of just about 70 MPa.

Download Full-text

Effects of mixing enthalpy and cooling rate on phase formation of AlxCoCrCuFeNi high-entropy alloys

Materialia ◽

10.1016/j.mtla.2019.100292 ◽

2019 ◽

Vol 6 ◽

pp. 100292 ◽

Cited By ~ 4

Author(s):

X.D. Xu ◽

S. Guo ◽

T.G. Nieh ◽

C.T. Liu ◽

A. Hirata ◽

...

Keyword(s):

Cooling Rate ◽

Phase Formation ◽

Mixing Enthalpy ◽

High Entropy Alloys ◽

High Entropy

Download Full-text

Alloy Designs of High-Entropy Crystalline and Bulk Glassy Alloys by Evaluating Mixing Enthalpy and Delta Parameter for Quinary to Decimal Equi-Atomic Alloys

MATERIALS TRANSACTIONS ◽

10.2320/matertrans.m2013352 ◽

2014 ◽

Vol 55 (1) ◽

pp. 165-170 ◽

Cited By ~ 21

Author(s):

Akira Takeuchi ◽

Kenji Amiya ◽

Takeshi Wada ◽

Kunio Yubuta ◽

Wei Zhang ◽

...

Keyword(s):

Mixing Enthalpy ◽

High Entropy ◽

Glassy Alloys

Download Full-text

Synthesis and Characterization of Novel High Entropy Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.978.167 ◽

2020 ◽

Vol 978 ◽

pp. 167-173

Author(s):

Anil Kumar ◽

B. Vinith ◽

Aditya Kumar Choudhary ◽

Manoj Kumar Chopkar

Keyword(s):

Mechanical Alloying ◽

Synthesis And Characterization ◽

Mixing Enthalpy ◽

Valence Electron Concentration ◽

High Entropy Alloys ◽

Face Centered Cubic ◽

High Entropy ◽

Cubic Structure ◽

Face Centered

High entropy alloys (HEAs) generally exhibit either high resistance to deformation or high toughness due to the presence of body-centered or face-centered cubic structure, respectively. To overcome these limitations, new high entropy alloys have been developed in the present study. This investigation aims to synthesis and characterization of novel CoCrFeNi3Si, CoCrFe2Ni2Si, and Co2CrFeNi2Si high entropy alloys. The mechanical alloying route is used to synthesize these alloys. Grinding was carried out to 20h and X-ray diffraction (XRD) analysis was done at different time intervals of grinding. The face-centered cubic structure along with the intermetallic compound of Ni-Si was observed after 20h of grinding. Furthermore, a pseudo binary strategy based on the valence electron concentration and mixing enthalpy is also employed to design the high entropy alloys considered in the present study. Carefully analysis of the XRD pattern indicates that from 5 to 20h of mechanical alloying there is a decrement in the initial peaks of elements observed.

Download Full-text