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The present work explores the design and development of Fe35-XCo10Ni25Cr15Mn5V10Nbx (x = 2.5, 5, 7.5, and 10 at. %) eutectic high-entropy alloys (EHEAs) using a combination of thermodynamic simulation and experimental approaches. The studied EHEAs consist of primary Fe–Ni–Cr-rich FCC solid solution phase and eutectic mixture between FCC solid solution phase and Nb-rich Fe2Nb-type C14 Laves phase. The microstructural feature of studied EHEAs varies from hypoeutectic to fully eutectic with an increase in the Nb concentration, and the microhardness increases with increasing Nb concentration. Furthermore, the hardness values of reported HEAs along with the studied EHEAs as a function of alloying elements are taken into consideration to establish an artificial neural network (ANN) model to predict the microhardness of EHEAs. The predicted results obtained are in good agreement with the experimental data having the correlation coefficient (R) of 0.9878 and an average absolute relative error (AARE) of 4.82%.

In the current investigation, nanocrystalline multicomponent high-entropy alloys (HEAs) have been synthesized in the Cu x Zn y Ti 20 Fe 20 Cr 20 system ( x / y  = 1/0, 3/1, 1; and x  +  y  = 40) by mechanical alloying and subsequently consolidated using spark plasma sintering (SPS) in argon atmosphere at a pressure of 50 MPa. A detailed X-ray diffraction and transmission electron microscopy study reveals the presence of both FCC copper solid-solution, (Cu) ss and BCC chromium solid-solution, (Cr) ss phases in both the mechanically alloyed powders as well as the sintered compacts. The phase formation and stability of the sintered multicomponent Cu x Zn y Ti 20 Fe 20 Cr 20 with x / y  = 3/1 and x  +  y  = 40 pellet have been studied at different sintering temperatures, i.e. , 873 K, 973 K, 1073 K, and 1173 K (600 °C, 700 °C, 800 °C, and 900 °C). The important findings include that high Vickers bulk hardness of around 6 GPa and relative density of around 95 pct reported in the Cu x Zn y Ti 20 Fe 20 Cr 20 with x / y  = 3/1 and x  +  y  = 40 HEAs, SPSed at 1173 K (900 °C). The formation, consolidation, and microstructural details are analyzed critically and discussed.

The present work is aimed at understanding the solidification pathways of the Ti-rich Ti-Fe-Co in situ composites consisting of ultrafine eutectic with micron-scale dendrites. The effect of addition of Co in the Ti-rich binary Ti-Fe alloys has been systematically investigated. The series of Ti-Fe-Co ternary alloys i.e. , Ti 75 Fe 25− x Co x ( x  = 0, 5, 10, 12.5, 15, 20), (Ti 70.5 Fe 29.5 ) 100− x Co x ( x  = 0, 2, 4, 6, 8, and 10), Ti 70 Fe 30− x Co x ( x  = 0, 5, 10, 15, 20, 25), Ti 65 Fe 35− x Co x ( x  = 0, 10, 15, 17.5, 20, 25), and Ti 60 Fe 40− x Co x ( x  = 0, 16, 18, 20, 22, 24) are synthesized by arc melting cum suction casting technique under high purity Ar atmosphere to obtain alloy cylinders having diameter ( ϕ ) of 3 mm. Detailed X-ray diffraction and electron microscopic (SEM and TEM) study are carried out to identify the phases as well as to monitor the sequence of phase evolution in the ternary alloys. The present study conclusively proves that the Ti 65 Fe 10 Co 25 , Ti 70 Fe 30− x Co x ( x  = 10, 20, 25), and Ti 75 Fe 15 Co 10 alloys show the ternary quasi-peritectic reaction of L + Ti(Co,Fe) → ( β -Ti) ss  + Ti 2 (Co,Fe) at invariant point P (=Ti 75.5±0.8 Fe 6.3±2.1 Co 18.2±2.7 ) which is cooperated by means of eutectic reaction of L → ( β -Ti) ss  + Ti 2 (Co,Fe) below P and peritectic reaction L + Ti(Co,Fe) → Ti 2 (Co,Fe) for Ti 65 Fe 10 Co 25 ,Ti 70 Fe 10 Co 20 , and Ti 70 Fe 5 Co 25 alloys or eutectic reaction L → ( β -Ti) ss +Ti(Co,Fe) for Ti 70 Fe 20 Co 10 , and Ti 75 Fe 15 Co 10 alloys above the point P. In addition, the peritectic reaction L + Ti(Co,Fe) → Ti 2 (Co,Fe) plays a significant role in the phase evolution. The microstructural evolution, phase equilibria and solidification pathways have been explained by generating liquidus projection of the investigated alloys. Interestingly, the Co addition leads to the formation of complex Ti 2 Co phase and significantly affects the compositional stability of TiFe phase. This is found to have significant influence on the microstructural development during suction casting of the investigated alloys.

The current work has been undertaken with an aim to investigate the phase evolution and mechanical behaviour of Ti–Fe–Co ternary alloys. Extensive electron microscopic studies have been carried out to identify the phases present in the microstructure of the suction cast Ti–Fe–Co ternary alloys. The SEM micrographs of the investigated Ti–Fe–Co alloys reveal that the microstructures consist of eutectic matrix (L → (β-Ti)ss + Ti(Fe,Co) and/or L→(β-Ti)ss + Ti2(Co,Fe)) along with different dendritic phases ((β-Ti)ss or Ti(Fe,Co), Ti2(Co,Fe)) depending on concentration of Co. Ti70Fe20Co10 and Ti75Fe15Co10 alloys show the bimodal eutectics, ((β-Ti)ss + Ti(Fe,Co)) and ((β-Ti)ss + Ti2(Co,Fe)). The room temperature uniaxial compressive test of the Ti70Fe20Co10 ternary alloy exhibits simultaneous improvement in compressive strength (~2819 MPa) and plasticity (~8.5%) among the series of investigated Ti–Fe–Co ternary alloys. Fractography of the surface of Ti70Fe20Co10 ternary alloy reveals mixed mode of fracture. The significant outcome of the investigated Ti–Fe–Co alloys is that, the plasticity of the alloys can be improved by the development of bimodal eutectics in the microstructure or by incorporating disordered dendritic phase.

The primary objective of the present study is to simulate the crevice corrosion for the first time in a single-phase face-centered cubic (FCC) Co 25 Cr 20 Fe 25 Ni 25 V 5 high entropy alloy (HEA) by finite element method including Tafel test for 72 and 168 h in a 2.4 M sodium chloride solution. This HEA has good galvanic degradation resistance with inferior degradation current per area of 1.1236 × 10 –4 Acm −2 for 168 h. The maximum simulated crevice corrosion rate is 0.978 mmpy and 17.335 mmpy and the maximum electrolyte potential at the end of crevice tip is 2.68 × 10 –4  V and 4.7 × 10 –3  V after a time span of 24 and 168 h. The studied single-phase HEA exhibits enhanced crevice corrosion resistance which is attributed to the formation of constitutionally uniform oxide layer of Cr, Ni, and V.

The present work explores the synthesis of nanocrystalline tungsten-containing AlCrFeMnNiWx (x= 0, 0.05, 0.1, 0.5 mol) high-entropy alloys (HEAs) by mechanical alloying with subsequent Spark Plasma Sintering (SPS) route. Microstructure, thermal stability, and mechanical properties of designed HEAs are critically analyzed and discussed. It is found that nanocrystalline HEA powders exhibit the presence of primary BCC solid solution phase, and the sintered HEAs at 900 °C show the formation of sigma rich tetragonal phase, ordered B2, BCC phase, and minor FCC solid solution phase. The designed HEAs exhibit excellent hardness (8.31-13.57 GPa) as well as high elastic modulus (165.52-202.3 GPa), which are strongly dependent upon the tungsten content.

FeCoNi medium entropy alloy was mechanically alloyed at two angular velocities, i.e., 500 and 300 rpm, utilizing a high-energy planetary ball mill. The energy transfer criteria, phase, and microstructural evolution during the milling mechanism were described and analyzed by kinematics, X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The results revealed that the total energy transferred during mechanical alloying was near ~ 4.635 times greater than FeCoNi-300 rpm. However, the structural analysis showed the γ-FCC phase in the case of FeCoNi-500 rpm and α-BCC + γ-FCC phases in case of FeCoNi-300 rpm. The magnetic properties were studied at 300 K and presented an excellent soft magnetic behavior with saturation magnetization of 124.86 emu/g and coercivity of 15.39 Oe in the case of FeCoNi-500 rpm. Furthermore, temperature-dependent magnetization measurements were also carried out and fitted with the modified Bloch model and Bloch and Curie–Weiss law-modified model. The results revealed that there is the existence of a significant ferromagnetic phase in the case of FeCoNi-300 rpm.

In the present work, the Arrhenius-type constitutive equation and artificial neural network (ANN) model have been used to predict the hot deformation behavior of CoFeMnNiTi eutectic high-entropy alloy in the temperature range 1073-1273 K and strain rate range 0.001-1 s−1. The performance of both models is assessed by using the coefficient of correlation (R) and average absolute relative error (AARE). The ANN model with R = 0.9997 and AARE = 1.52 % better predicts flow behavior than the Arrhenius type model with R = 0.9769 and AARE = 11.5 %. The rate of softening and mean free path value are also evaluated at different thermomechanical conditions to understand the deformation mechanism. The compressive flow behavior of EHEA also studied and understood the softening and globularization phenomenon during deformation and proposed the deformation mechanism.

NiCoFe(SiMn) x high entropy amorphous alloys (HEAAs) were successfully prepared via mechanical alloying. The structural and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer. Based on the structural analysis, a simple solid solution of α-BCC + γ-FCC phases were formed for x = 0.0 , 0.1 , whereas γ-FCC + amorphous phases were detected as Si and Mn content increases for x = 0.25 , 0.5 , 0.75 , 1.0 HEAAs. Furthermore, differential scanning calorimetry was used to examine the non-isothermal crystallization kinetics in the 35 h milled sample. The results showed that the HEAAs powder has two distinct exothermic crystallization peaks, which become much more prominent as Si and Mn content increases. The onset (E x1 , E x2 ) and the apparent (E p1 , E p2 ) activation energies were calculated using Kissinger's and Ozawa's equations. According to these equations E x 1  >  E p 1 , E x 2  >  E p 2 for the proposed HEAAs, the nucleation process was more difficult than overcoming the energy barrier for the rearrangement of atoms and the grain growth process of crystallization. Meanwhile, local activation energies gave consistent results with the apparent activation energies. They estimated from the Kissinger–Akahira–Sunose, and Ozawa-Flynn-Wall models under non-isothermal conditions, revealing that both the exothermic peaks have higher values of local activation energies at the beginning of the crystallization process. In addition, the Johnson–Mehl–Avrami-Kolmogorov models were used to determine the Avrami exponents, indicating that the crystallization process becomes more accessible due to decreased local activation energies, leading to high-dimensional growth with an increasing nucleation rate. Moreover, a simple phenomenological model was also proposed based on the Lorentzian functions model evaluated on the first derivative of magnetic hysteresis loops. Graphical Abstract

For the first time, the numerical simulation to understand the solidification phenomena during suction casting of single-phase six component Fe–Co–Cr–Ni–V–Al FCC HEA is reported here along with the experimental validation and comparison with thermodynamic simulation using CALPHAD approach. The present study elaborates the complete information about solidification behavior, distribution of temperature in metal casting and heat transfer in metal casting and metal-mold interface and mold to the environment and phase transformation mechanism during solidification. The simulated results are validated with the experimental measured hardness using a micro-Vickers hardness tester at 500 g load and the measured hardness of the FCC HEA varies from 220 ± 2.98 to 259 ± 5.95 HV. The developed simulation model is in good agreement and acceptable with the experimental results and thermodynamic simulation results.