Face-centered Cubic Research Articles

Vacuum brazing of Al0.3CoCrFeNi high-entropy alloys with CoCrFeNiNb0.5 eutectic filler metal for wide-temperature range application

The service conditions of high-entropy alloys (HEAs) joints brazed with conventional filler metals (FMs) can be confined because few HEAs phases generate in the braze zone. In this study, a multicomponent CoCrFeNiNb0.5 eutectic HEAs (EHEAs) FM was developed to braze Al0.3CoCrFeNi HEAs in vacuum, the braze zone mainly consisted of face-centered cubic (FCC) and Laves lamellar structure, exhibiting a superior metallurgical compatibility with the Al0.3CoCrFeNi base metals (BMs). The shear strength and shear displacement of brazed joints reached 461 MPa/1.35 mm at room temperature (RT), 741 MPa/1.42 mm at -196 °C and 380 MPa/1.62 mm at 700 °C, respectively. This strategy can stimulate the fabrication and wide-temperature range applications of HEAs brazed components by exploiting the structural and performance merits of EHEAs FMs.

Improving strength-ductility balance of a brittle Al-doped FeCrNi multi-principal element alloy by introducing a heterostructure with hard phase enveloping soft phase

In the present work, a heterostructure was created in a brittle Al-doped FeCrNi multi-principal element alloy via thermomechanical treatment. This heterostructure consists of a hard phase surrounding a soft phase, with the soft defect-free face-centered cubic (FCC) phase formed through phase transformation evenly distributed within the hard body-centered cubic (BCC) matrix. This unique heterostructure promotes more uniform deformation, thereby enhancing the deformability of the original hard BCC matrix. As a result, the elongation was increased from 2.4% to 17%, while the ultimate tensile strength was just decreased from 1076 MPa to 1021 MPa. The maintenance of strength is primarily attributed to the hetero-deformation-induced (HDI) strengthening effect provided by this distinctive heterostructure. Overall, this special heterostructure formed through phase transformation opens up new possibilities for developing alloys with both high strength and ductility.

Design of novel structural eutectic high entropy alloys (EHEAs) containing high-temperature resistant alloying elements

This article employs the “Simple Mixing Enthalpy Method” to add high-temperature alloying elements Mo/V and Nb to the Fe-Co-Cr-Ni-based alloy system, and utilizes a model of the relationship between elements and phase structures. Finally, EHEAs are successfully designed with the help of phase diagrams, namely FeCoNi2.0Cr1.2Mo0.2Nb0.63 (Mo0.2Nb0.63) and FeCoNi2.0Cr1.2V0.2Nb0.68 (V0.2Nb0.68). In EHEAs, a typical fully eutectic microstructure is observed, consisting of alternating FCC (face-centered cubic) and HCP (hexagonal close-packed) phases. Evaluation of mechanical performance indicators reveals that nano-hardness and elastic modulus increase from the FCC phase to the HCP phase, while the hardness and elastic modulus of the eutectic phase originate from modulation of these two phases. Meanwhile, the microhardness of both alloy systems increases linearly with increasing Nb content. In addition, EHEAs exhibit high strength and ductility but with differences attributed to the significant influence of Mo and V elements on eutectic phase spacing and phase size. Different phase interface types and strain gradients during deformation affect the mechanical properties. This study tests the high-temperature compression performance and fracture morphology of novel high-entropy alloys, paving the way for subsequent research on high-temperature performance.

Brownian dynamics simulation of the structural evolution in monodisperse hard-sphere suspensions during drying and sedimentation processes.

The drying behavior of monodisperse colloidal films, with a focus on the influence of process variables on film microstructures, is explored via Brownian dynamics (BD) simulations. In our model, hard-sphere colloidal particles are dispersed in a Newtonian liquid with an initial particle volume fraction of 0.1. The effects of the drying rate and sedimentation on the evolving microstructures are systematically investigated using two dimensionless numbers: the Péclet number (Pe), which represents the competition between evaporation and diffusion, and the sedimentation number (Ns), which reflects the relative influence of sedimentation on evaporation. First, we analyze the local particle volume fraction and film structure at various Pe and Ns. As Pe increases, particle accumulation occurs near the liquid-gas interface, whereas a high Ns promotes dense packing near the substrate owing to sedimentation. The BD simulation results, viz. the local volume fraction profiles and drying regime maps, are in good agreement with those of the continuum model proposed by Wang and Brady. Structural analysis of the dried films reveals that at a low Pe (Pe = 0.1), a face-centered cubic (FCC) structure dominates, primarily independent of the sedimentation effects. In contrast, a high Pe leads to hexagonal close-packed or amorphous structure formation. Notably, at intermediate drying rates (Pe = 10), an increase in Ns promotes additional FCC ordering in the final film structure. Our study provides new insights into the hitherto underexplored role of sedimentation in the structural evolution of drying colloidal films, revealing the mechanisms of drying-induced assembly in colloidal systems.

Influence of Cold Drawing on Phase Transformation and Tensile Properties of FeCrMn Austenitic Stainless Steel 201

Manganese stabilizes the austenite and reduces the stacking fault energy in face‐centered cubic (FCC) structures, promoting the formation of hexagonal and cubic structures. This study investigates the phase transformation and mechanical behavior of extremely low‐carbon FeCrMn austenitic stainless AISI 201 steel subjected to cold drawing in three stages, ultimately reaching a true strain of 0.93. The objective is to examine the transformation from the parent FCC structure to hexagonal close‐packed and body‐centered cubic structures as a combination of transformation‐induced plasticity and twinning‐induced plasticity phenomena. X‐ray diffraction and electron backscatter diffraction analyses are utilized to investigate phase transformations under significant plastic deformation and the crystallographic orientation relationships between phases. Additionally, tensile and hardness tests are performed to assess the impact of plastic deformation on mechanical properties. Results indicate that a true strain of 50% is optimal for balancing strength and ductility in CrMnFe austenitic stainless steel. After applying a true strain of ε1 = 26.7%, yield strength (YS) increases by 192% and ultimate tensile strength (UTS) by 35%, while elongation reduces by 41%. With a further strain of ε2 = 57.5%, YS increases by 71% and UTS by 44%, but elongation drastically decreases by 94%. Applying the final strain of ε3 = 94.0%, YS and UTS only increase by 3% and 2%, respectively, while elongation further reduced by 40%. These findings suggest that a true strain of 50% shall be considered the maximum reduction for maintaining a balance between strength and ductility in CrMnFe austenitic stainless steel.

SILVER NANOPARTICLES-AQUEOUS LEAF EXTRACT OF SIDAGURI (SIDA RHOMBIFOLIA) AS REDUCING AGENTS

The Sidaguri leaf, scientifically known as Sida rhombifolia, is a plant species rich in flavonoids that have the ability to act as reducing agent in formation of silver nanoparticles. This study presented the synthesis of silver nanoparticles (AgNp-Sid) using aqueous leaf extract of sidaguri. This study utilized a concentration ratio of 2:90 mL aqueous leaf extract of Sidaguri and AgNO3 1 mM. The size and morphology of AgNp-Sid was measured using UV-Visible Spectrophotometer, PSA, FT-IR, SEM-EDS, and XRD. The investigation revealed an ordinary particle size of 63.5 nm with polydispersity index (PI) of 0.284. The maximum wavelength varies between 405.4 nm and 407.8 nm with the increasing of time. AgNp-Sid exhibited a spherical morphology and had a crystalline structure that is face-centered cubic. The results suggested that the aqueous leaf extract of sidaguri had the ability to function as a reducing agent in the synthesis of silver nanoparticles, offering a safe, cost-effective, and environmentally friendly alternative.

Unconventional Hexagonal Close-Packed High-Entropy Alloy Surfaces Synergistically Accelerate Alkaline Hydrogen Evolution.

Accelerating the alkaline hydrogen evolution reaction (HER), which involves the slow cleavage of HO-H bonds and the adsorption/desorption of hydrogen (H*) and hydroxyl (OH*) intermediates, requires developing catalysts with optimal binding strengths for these intermediates. Here, the unconventional hexagonal close-packed (HCP) high-entropy alloy (HEA) atomic layers are prepared composed of five platinum-group metals to enhance the alkaline HER synergistically. The breakthrough is made by layer-by-layer heteroepitaxial deposition of subnanometer RuRhPdPtIr HEA layers on the HCP Ru seeds, despite the thermodynamic stability of Rh, Pd, Pt, and Ir in a face-centered cubic (FCC) structure except for Ru. The synchrotron X-ray absorption spectroscopy (XAS) confirms the atomic mixing and coordination environment of HCP RuRhPdPtIr HEA. Most importantly, they exhibit notable improvements in both electrocatalytic activity and durability for the HER in an alkaline environment, as compared to their FCC RuRhPdPtIr counterparts. Electrochemical measurements, operando XAS analysis, and density functional theory unveil that the binding strengths of H* and OH* intermediates on the active Pt and Ir sites can be weakened and strengthened to a moderate level, respectively, by mixing non-active Ru, Rh, and Pd atoms with Pt and Ir atoms within the HCP HEA with strong synergistic electronic effects.

Exceptional tensile ductility and strength of a BCC structure CLAM steel with lamellar grains at 77 kelvin

The low-temperature tensile brittleness of body-centered cubic (BCC) metals and alloys can seriously compromise their service applications. In this study, we prepared a BCC structured China low activation martensitic steel (CLAM) steel with lamellar grains by regulating the rolling and heat-treatment processes, successfully reversing the decreasing trend of ductility in the steel with decrease in temperature. Compared with current face-centered cubic (FCC) structural steels and high-entropy alloys, the lamellar grained CLAM steel exhibits an excellent synergy of strength and ductility at 77K, but with lower raw material costs. The superior low temperature ductility of the lamellar grained steel can be attributed to an increase in grain strength at low temperatures which promotes the propagation of layered tearing cracks; this in turn leads to a significant increase in the necking area of the steel, thereby compensating for the decrease in ductility. We conclude that our lamellar grain structures can be utilized to significantly enhance the low-temperature tensile ductility of BCC metals and alloys, thereby expanding their service range to cryogenic temperatures.

Deformation mechanism of a metastable medium entropy alloy strengthened by the synergy of heterostructure design and cryo-pre-straining

Face-centered cubic (FCC) medium entropy alloys (MEAs) have received considerable attention due to their impressive mechanical properties and responses. However, their practical application is limited by their modest yield strengths. The potential enhancement of the mechanical properties of single-phase MEAs was explored in this study through a synergistic approach combining heterogeneous structure design with subsequent cryo-pre-straining. A heterogeneous lamella structure was produced in a single-phase Fe55Mn20Cr15Ni10 MEA via two-step rolling and annealing. Cryo-pre-straining at varying degrees (6, 12, 21, and 36%) introduced hexagonal close-packed (HCP) phase, high-density dislocations, twins, and stacking faults, leveraging the reduced stacking fault energy at cryogenic temperatures. This process enhanced the alloy's yield strength from 353 MPa to 1.2 GPa (compared to the baseline uniform coarse-grained structure), while maintaining an acceptable total elongation of 8.4%. The impact of cryo-pre-straining on the microstructure and mechanical properties of the MEA was assessed using in-situ synchrotron X-ray diffraction analysis. Cryo-pre-straining (36%) achieved a higher dislocation density (6.1 × 1015 m−2) compared to room-temperature straining (2.5 × 1015 m−2). The stress contribution from HCP-martensite and the evolution of dislocation density during loading were quantified, along with observations of negative stacking fault probability and strain-induced HCP→FCC reverse transformation in cryo-pre-strained samples under loading conditions. Furthermore, the contributions of regulated microstructures to the enhancement of yield strength were quantitatively assessed.

Liquid and gas permeabilities of nanostructured layers: Three-dimensional lattice Boltzmann simulation

Liquid water and gas permeabilities in nanostructured catalyst layers (CLs) (pore size ∼10–150 nm) and microporous layers (MPLs) (pore size ∼50 nm-5 μm) are crucial to reduce the mass transport loss in proton exchange membrane fuel cells (PEMFCs). Experimental measurement of their permeabilities poses great challenges due to their brittle and thin characteristics. Presently, considerable discrepancy exists in the reported permeability values for CLs and MPLs in the literature with variation spanning several orders of magnitude. This study digitally reconstructed various nanostructures of similar pore size as CLs and MPLs to calculate their permeabilities using the Lattice Boltzmann Method (LBM) based on no-slip (e.g. for liquid water flow in MPL and CL's secondary pores) or slip condition (e.g. for gas flow in MPL). Analysis was performed to evaluate the range of pore size in nanostructures for the two boundary conditions. A comprehensive investigation was conducted under various parameters such as the Reynolds number (Re), sphere diameter, porosity, and pore structure. The results revealed that permeability exhibits an increasing trend with the diameter and porosity. The predicted permeability of randomly arranged spheres agrees well with established correlations. The random sphere structure demonstrates higher permeability than their body-centered cubic (BCC) and face-centered cubic (FCC) counterparts. Under slip boundary condition, the permeability was enhanced, compared to the no-slip condition. This study's novelty lies in using distinct boundary conditions to assess the permeabilities of liquid and air, based on flow pattern analysis in the CL and MPL pore structures. A new empirical correlation describing the influence of the Knudsen number (Kn) on the slip permeability was developed, exhibiting consistency with simulation across the entire porosity spectrum.

Enhancing the Mechanical Properties of Co-Cr Dental Alloys Fabricated by Laser Powder Bed Fusion: Evaluation of Quenching and Annealing as Heat Treatment Methods.

Residual stresses and anisotropic structures characterize laser powder bed fusion (L-PBF) products due to rapid thermal changes during fabrication, potentially leading to microcracking and lower strength. Post-heat treatments are crucial for enhancing mechanical properties. Numerous dental technology laboratories worldwide are adopting the new technologies but must invest considerable time and resources to refine them for specific requirements. Our research can assist researchers in identifying thermal processes that enhance the mechanical properties of dental Co-Cr alloys. In this study, high cooling rates (quenching) and annealing after quenching were evaluated for L-PBF Co-Cr dental alloys. Cast samples (standard manufacturing method) were tested as a second reference material. Tensile strength, Vickers hardness, microstructure characterization, and phase identification were performed. Significant differences were found among the L-PBF groups and the cast samples. The lowest tensile strength (707 MPa) and hardness (345 HV) were observed for cast Starbond COS. The highest mechanical properties (1389 MPa, 535 HV) were observed for the samples subjected to the water quenching and reheating methods. XRD analysis revealed that the face-centered cubic (FCC) and hexagonal close-packed (HCP) phases are influenced by the composition and heat treatment. Annealing after quenching improved the microstructure homogeneity and increased the HCP content. L-PBF techniques yielded superior mechanical properties compared to traditional casting methods, offering efficiency and precision. Future research should focus on fatigue properties.

Enhancement on mechanical properties via phase separation induced by Cu-added high-entropy alloy fillers in metastable ferrous medium-entropy alloy welds

This study evaluated the weldability of metastable ferrous medium-entropy alloys using high-entropy alloy fillers with various Cu contents and elucidated the strengthening mechanisms at room and cryogenic temperatures by focusing on the formation of a Cu-rich phase (FCC2) in the weld metal (WM). The WM with higher Cu content exhibited more dual face-centered cubic (FCC) phases with dendrite-shaped compositional heterogeneity due to phase separation driven by higher mixing enthalpy. The FCC2 induced greater lattice distortion, resulting in higher nano-hardness and stronger solid-solution hardening. In addition, the increased presence of FCC2 in the WM promoted grain refinement and the formation of additional grain boundaries within individual grains. After cryogenic deformation, the base metal and heat-affected zone in transverse welds underwent martensitic transformation from metastable FCC (transformation-induced plasticity), while the diluted WMs exhibited twinning-induced plasticity because of their higher stacking fault energy (SFE) compared to the base metal. The combination of these deformation mechanisms enhanced the cryogenic tensile properties without compromising ductility. Furthermore, the cryogenic tensile properties of weld with higher Cu content were further improved due to the increased formation of deformation twins in the WM. The consumption of solute Cu to form more Cu-rich FCC2 resulted in compositional variations in the matrix (FCC1), leading to a further reduction in the SFE of FCC1 and the activation of additional twin formation. Additionally, FCC2 with a relatively higher SFE refined secondary twins as well as contributed to further dislocation accumulation. This study suggests that the formation of Cu-rich phase in the WM can enhance mechanical properties at both room and cryogenic temperatures and provides a valuable approach for the future development of welding materials to improve the mechanical properties of FCC-based welded structures.

Evolution of tool wear and machining quality during dry milling of AlCoCrFeNi2.1 eutectic high entropy alloy

AlCoCrFeNi2.1, a new class of eutectic high entropy alloy (EHEA) has drawn significant interest owing to the lamellar structure of alternating face-centered cubic (FCC) and B2 phases. Properties such as high strength and high plasticity render the machining of this alloy challenging. Addressing this issue, the milling experiments were conducted under dry conditions to investigate the machining quality of AlCoCrFeNi2.1 EHEA as well as the tool wear. The cutting temperature and cutting force were measured to explain the changes in tool wear and machining quality. The tool wear mechanisms and evolution modes were clarified. Finally, the change of surface roughness and surface morphology under different parameters were analyzed and the characterization method of plastic flow marked by B2 phase was proposed. Results showed that both the cutting temperature and cutting force increase as the milling parameters become larger. The width of flank wear increases with the increase of the cutting speed and the feed rate when the volume of material removal volume is constant. The tool wear modes evolved differently with different cutting parameters, for instance, abrasive wear dominated while the cutting speed was less than 80 m/min, but for higher speeds up to 110 m/min, adhesive wear and coating peeling occurred. As the cutting speed increases further, crater wear on the rake face starts to arise in addition to the flank wear. Abrasive wear and adhesive wear with increasing feed rate were dominant until a certain threshold (0.10 mm/tooth) beyond which the coating peels off the tool. Furthermore, chipping occurred for a higher feed rate of 0.14 mm/tooth. In particular, the formation of tool adhesive wear is mainly caused by the FCC phase adheres. In terms of machining quality, larger cutting parameters will worsen the surface roughness and morphology as well as lead to deeper subsurface plastic flow. The research will be conducive to promoting the applications of AlCoCrFeNi2.1 HEA.

Corrosion studies of Al-Mg-Sc-Zr Alloy with Low Sc/Zr ratio fabricated by laser powder bed fusion for marine environments

This study investigates the corrosion behavior of a laser powder bed fusion (LPBF) Al-Mg-Sc-Zr alloy with a Sc/Zr ratio of less than 1 in 3.5wt% NaCl solution. X-ray diffraction (XRD) analysis revealed the presence of an Al matrix with face-centered cubic (FCC) structure and the secondary phase Al3(Sc,Zr) with L12 crystal structure. Microstructural analysis indicated a bimodal grain size distribution with fine equiaxed and columnar grains influenced by thermal gradients and secondary phase Al3(Sc,Zr). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5wt% NaCl solution demonstrated that the alloy exhibits a less negative corrosion potential (Ecorr) and lower corrosion current density (icorr) compared to other Al-Mg-Sc-Zr alloys with higher Sc/Zr ratios, indicating superior corrosion resistance. The enhanced performance is attributed to the fine grain structure and the formation of a stable protective oxide layer facilitated by the higher Zr content.

Impact of gradient microstructure on strain hardening via activation of multiple deformation mechanisms in CoCrNi medium entropy alloy

Abstract Face centered cubic (FCC) structural medium/high entropy alloys (MEAs), characterized by excellent strength and ductility, have attracted significant attention by the research community. The incorporation of gradient structures (GSs) further can enhance their mechanical properties. In the present research, we employ the rotation acceleration shot peening technique to introduce a GS within the CoCrNi FCC MEA to investigate underlying mechanisms governing the physical deformation processes during the generation of GSs through processing, which the primary goal is mitigating the intrinsic trade-off between strength and ductility. Through the microstructures analysis along the depth direction, both pre and post uniaxial tensile plastic deformation, we unveiled that the low stacking fault (SF) energy characteristic of the CoCrNi MEA triggered the emergence of diverse defects in the core region. The presence of nanoscale deformation twins, SFs, Lomer–Cottrell dislocation locks and phase transformation from FCC to hexagonal close-packed at twin boundaries synergistically enhanced the strain hardening capacity of the material.

Optimizing toughness in high entropy alloys using a genetic algorithm: A combined computational and experimental approach

A genetic algorithm (GA) was developed to search for high entropy alloys (HEAs) with good combinations of mechanical properties. The algorithm was designed find single-phase face-centered cubic (FCC) HEAs, already known for their ductility, with high Hall-Petch constants (K) and high critical resolved shear stresses (τY). The objective was to develop a methodology that allows the design of HEAs in a multi-objective environment, focusing on alloys that exhibit enhanced ductility and strength, achieved through an increase in its yield point without significant loss of its ultimate deformation via adjustments of K and τY values, resulting in an alloy with high toughness. The most promising alloy suggested by the genetic algorithm was an unconventional composition (Co32.73Cu15.11Fe0.72Hf0.72Mn35.97Mo3.96Ni10.43Sn0.36), with eight different elements in non-equiatomic ratios with maximized K and τY values. This alloy was then experimentally produced and characterized by scanning electron microscopy (SEM), synchrotron x-ray diffraction (XRD), transmission electron microscopy (TEM) and microhardness, with the objective of validating the predictions made by the GA. An advantage of the proposed method is the possibility of more systematically identifying and exploring new compositions in the complex composition space characteristic of these multicomponent alloys, as it directs its search towards domains that can be used to solve challenging problems involving multi-objective optimization. However, the thermodynamic parameters used for single-phase FCC prediction, namely the valence electron concentration (VEC) and the dimensionless thermodynamic parameter φ, exhibited limitations. These limitations were further explored in the present study, as evidenced by the fact that the microstructure of the selected alloy was not single-phase, which hindered the study of the mechanical properties, predicted exclusively for monophasic FCC alloys. Therefore, this work highlights the necessity for the development of novel thermodynamic equations for phase prediction, or even the integration of the genetic algorithm with other methodologies, such as CALPHAD calculations, to achieve enhanced results.

Influence of Al and Ti Alloying and Annealing on the Microstructure and Compressive Properties of Cr-Fe-Ni Multi-Principal Element Alloy

This study meticulously examines the influence of aluminum (Al) and titanium (Ti) on the genesis of self-generated ordered phases in high-entropy alloys (HEAs), a class of materials that has garnered considerable attention due to their exceptional multifunctionality and versatile compositional palette. By meticulously tuning the concentrations of Al and Ti, this research delves into the modulation of the in situ self-generated ordered phases’ quantity and distribution within the alloy matrix. The annealing heat treatment outcomes revealed that the strategic incorporation of Al and Ti elements facilitates a phase transformation in the Cr-Fe-Ni medium-entropy alloy, transitioning from a BCC (body-centered cubic) phase to a BCC + FCC (face-centered cubic) phase. Concurrently, this manipulation precipitates the emergence of novel phases, including B2, L21, and σ. This orchestrated phase evolution enacts a synergistic enhancement in mechanical properties through second-phase strengthening and solid solution strengthening, culminating in a marked improvement in the compressive properties of the HEA.

Tuning the physical properties of ternary alloys (NiCuCo) for in vitro magnetic hyperthermia: experimental and theoretical investigation

Most of published research on magnetic hyperthermia focused on iron oxides, ferrites, and binary alloy nanostructures, while the ternary alloys attracted much limited interest. Herein, we prepared NiCuCo ternary alloy nanocomposites with variable compositions by mechanical alloying. Physical properties were fully characterized by XRD, Rietveld analysis, XPS, SEM/EDX, TEM, ZFC/FC and H-M loops. DFT calculations were used to confirm the experimental results in terms of structure and magnetism. The results showed that the fabricated nanoalloys are face centered cubic (FCC) with average core sizes of 9–40 nm and behave as superparamagnetic with saturation in the range 4.67–42.63 emu/g. Langevin fitting corroborated the superparamagnetic behavior, while law of approach to saturation (LAS) was used to calculate the magnetic anisotropy constants. Heating effciencies were performed under an alternating magnetic field (AMF, H0 = 170 Oe and f = 332.5 kHz), and specific absorption rate (SAR) values were determined. The highest magnetic saturation (Ms), heating potentials, and SAR values were attained for Ni35Cu30Co35 containing the lowest Cu but highest Ni and Co percentages, and the least for Ni15Cu70Co15. Importantly, the nanoalloys reached the required temperatures for magnetic hyperthermia (42 °C) in relatively short times. We also showed that heat dissipiation can be simply tuned by changing many parameters such as concentration, field amplitude, and frequency. Finally, cytotoxicity viability assays against two different breast cancer cell lines treated with Ni25Cu50Co25 nanoalloy in the presence and absence of AMF were investigated. No significant decrease in cancer cell viability was observed in the absence of AMF. When tested against tumorigenic KAIMRC2 breast cancer cells under AMF, the NiCuCo nanoalloy was found to be highly potent to the cells (~ 2-fold enhancement), killing almost all the cells in short times (20 min) and clinically-safe AC magnetic fields. These findings strongly suggest that the as-prepared ternary NiCuCo nanoalloys hold great promise for potential magnetically-triggered cancer hyperthermia.

Study on the Microstructure, Mechanical Properties, and Corrosion Behavior of 900 °C-Annealed CoCrFeMnNiSix (X = 0, 0.3, 0.6, 0.9) High-Entropy Alloys

In this study, a series of CoCrFeMnNiSix (x = 0, 0.3, 0.6, 0.9) high-entropy alloys (HEAs) were prepared by suspension melting of cold crucible, annealed at 1000 °C, and then quenched at 900 °C. The changes in the microstructure of the HEAs after the addition of Si were analyzed using X-ray diffraction (XRD), metallographic microscope, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The hardness, room-temperature friction, and wear behavior, room-temperature compressive properties, and corrosion resistance of the annealed CoCrFeMnNiSix HEAs were also studied. The results show that when the Si content is 0 and 0.3, the annealed CoCrFeMnNiSix HEA exhibits a single face-centered cubic (FCC) structure. As the silicon content increases, a face-centered orthorhombic (FCO) phase appears. At a Si content of 0.9, a hexagonal close-packed (HCP) phase is observed. After heat treatment, the hardness of the CoCrFeMnNiSix HEAs increases continuously with the addition of Si. The HEA with a Si content of 0.9 achieves the highest hardness of 974.8 ± 30.2 HV. The HEA with a Si content of 0.6 reaches the highest compressive strength and yield strength, which are 1990.3 MPa and 1327.5 MPa. When the Si content is 0.9, the HEA shows the smoothest surface after wear, with the best wear resistance, achieving a value of 0.21 mm−1. In the CoCrFeMnNiSix HEAs after 900 °C heat treatment, the HEA with a Si content of 0.6 exhibits the lowest self-corrosion current density of 0.23 µA/cm2 and the highest pitting potential of 157.65 mV, indicating the best corrosion resistance.

Microstructure, mechanical properties, and shape memory behavior of laser-directed energy deposited Co–20Fe–18Cr–19Mn high-entropy alloy

Laser additive manufacturing has become a powerful tool in modern production processes, and the additive manufacturing of Cantor-type high-entropy alloys has attracted considerable attention owing to its unique properties. In this study, we successfully utilized a laser-directed energy deposition (L-DED) process to fabricate a Co–20Fe–18Cr–19Mn, wt.% (Co40Fe20Cr20Mn20, at.%) alloy and analyzed its microstructure, room temperature mechanical properties, and shape memory effect. Microstructural analysis revealed a dense microstructure of the alloy. Before heat treatment, the alloy exhibited a microstructure consisting of both columnar and equiaxed dendrites with a hexagonal close-packed structure (HCP). However, post-treatment led to a completely different microstructure owing to recrystallization with a face-centered cubic (FCC) structure. Tensile testing results indicated a subtle anisotropy in the yielding, and after heat treatment, a significant enhancement in ductility was observed. A study of the shape memory effect demonstrated that the as-printed samples exhibited an FCC-HCP dual-phase structure, which transformed into an FCC single-phase structure after heat treatment. The application of external loading induced reformation of the HCP phase, successfully demonstrating the shape memory effect in the alloy, with a maximum recovery strain of 0.79 %.