Cubic Crystal Research Articles

Influence of design parameters on natural convection heat transfer in additively manufactured body centered cubic lattice structures

The natural convection heat transfer mechanism of the body centered cubic (BCC) lattice structure needs to be clarified for its application in passive cooling thermal management. The BCC lattice heat sinks with various design parameters, such as strut diameter and unit cell length, were fabricated using the laser powder bed fusion process. Subsequently, the thermal performance was experimentally determined for variations in design parameters. The thermal performance tended to be maximized when the relative density of the lattice heat sink constituted approximately 10 %. The numerical analysis was performed to figure out the heat transfer mechanism and investigate the effects of inclination angles. According to numerical results, a lattice heat sink with a smaller strut diameter at the given unit cell length entrains more air than one with a larger strut diameter. However, decreasing strut diameter led to a negative impact on conduction and radiation heat transfer due to the reduction in solid region and surface area. Depending on the inclination angle, thermal performance of a lattice heat sink proportionally decreases. The main cause of performance degradation was the hindrance of plume motion by the base of the heat sink.

Experimental investigation on energy absorption capability of 3D-printed lattice structures: Effect of strut orientation

This experimental study aimed to investigate the effect of strut orientation in various lattice structures that were created using 3D printers on the energy absorption capabilities of the structures. The experiment involved producing three different lattice structures, namely a cube lattice with vertical and horizontal struts, an octet structure with horizontal and 45˚ angled struts, and a body-centered-cubic (BCC) lattice structure with horizontal, vertical, and 45˚ angled struts using the FDM method. Nylon filament mixed with chopped carbon fiber was utilized as filament, and each lattice structure was designed to contain three units in the x and y directions and one and three units in the z-direction. The study conducted axial crushing tests on single-layer and three-layer lattices to determine the energy absorption capabilities of the various lattice structures. The octet lattice demonstrated the highest energy absorption in both single-layer and three-layer samples, making it the most efficient sample. In single-layer lattice samples, the cube and octet structures absorbed 77% and 94% more energy than the BCC structure, which absorbed only 12.8 J. However, the cube structure demonstrated the lowest energy absorption in three-layer samples. This was attributed to the buckling behavior seen in the strut of the lattice structure under axial load. The octet structure had the highest specific energy absorption value in both layers, making it the most energy-efficient sample.

Strength Weakening and Phase Transition Mechanisms in Nanoindentation of Al/Mg-Layered Nanocomposites: A Molecular Dynamic Study

Molecular dynamics (MD) simulations were performed to investigate the nanoindentation behavior of Al/Mg-layered nanocomposites with varying layer thicknesses and Mg layer orientations in this study. The aim is to understand the weakening mechanisms at low layer thicknesses and the phase transition mechanisms associated with the dislocation slip angle in the Mg layer. Results indicate that the nanoindentation strength of nanocomposites increases with the layer thickness in the range of 1–10 nm, with the strength of 9.5 × 10−7 N at 10 nm being approximately 73% higher than that at 1 nm. This strength increase is mainly attributed to high interfacial stress, the higher percentage of amorphous atoms, weakened interatomic interactions, and the transition of adjacent interfaces to fully coherent interfaces that significantly reduce their ability to hinder dislocations at the low-layer thickness range. Additionally, in the initial deformation process, the hexagonal close-packed (HCP) phase of the Mg layer firstly transforms into the body-centered cubic (BCC) phase due to its lower energy barrier, followed by the emergence of a faced-centered cubic (FCC) phase driven by 1/3<1−100> dislocations. In the late stage of deformation, new dislocations are generated in the FCC phase and move along its slip planes, altering the dislocation direction. The FCC/HCP interfacial configuration also affects the HCP phase transition mechanism in the Mg layer. When the dislocation slip angle is 0°, the primary phase transition is the BCC phase, whereas a 45° slip angle results in the FCC phase. These findings will provide a guide for the preparation and manufacturing of new high-quality layered nanocomposites.

Effect of oxygen on the microstructure, tensile properties and deformation behaviours of a biocompatible Ti40Zr25Nb25Ta10 high entropy alloy

The effect of oxygen on the microstructure, mechanical properties and deformation behaviours of as-cast biocompatible Ti40Zr25Nb25Ta10Ox (x = 0.5, 1.0 and 2.0 at.%) high entropy alloys (HEAs) was investigated. All three oxygen-doped HEAs solidified as a single body-centred cubic (BCC) phase grain structure with predominantly high-angle grain boundaries following the Mackenzie prediction. Increasing oxygen content significantly increased tensile strength at a rate of about 180 MPa/1.0 at.%, but decreased tensile ductility. However, at the addition level of 0.5 at.% O, the as-cast Ti40Zr25Nb25Ta10O0.5 HEA can achieve a yield strength (σ0.2) of 947 ± 44 MPa and an elongation at break (εf) of 9.5 % ± 1.8 %. These properties make this HEA comparable to medical grade Ti-6Al-4V (wt.%) alloy (ASTM Grade 23 titanium) (σ0.2 ≥ 759 MPa; εf ≥ 10 %) in its ability to absorb energy in plastic deformation, while offering greater resistance to permanent shape changes. Due to the possible strong interaction between oxygen atoms and dislocations through pinning and de-pinning, all oxygen-doped HEAs exhibited discontinuous yielding, whereas the low oxygen base HEA underwent normal yielding. No oxygen clusters were detected through atom probe tomography (APT) analysis. The deformation mechanism depends on oxygen content. The plastic deformation of the Ti40Zr25Nb25Ta10O0.5 HEA occurred through the formation of primary and secondary shear bands. In contrast, planar slip bands and a limited number of primary shear bands (without secondary shear bands) were observed in the Ti40Zr25Nb25Ta10O2.0 HEA. To ensure sufficient ductility, the oxygen content should be limited to 0.5 at.%. Furthermore, at this oxygen content, the corrosion resistance of the Ti40Zr25Nb25Ta10O0.5 HEA in Hank's solution is comparable to that of Ti-6Al-4V.

An excellent combination of strength and ductility via hierarchical precipitation structures in Co-free medium-entropy alloys

A Co-free non-equiatomic Ni2·5CrFeAl0·25Ti0.25 medium-entropy alloy (MEA) with an excellent strength-ductility synergy was fabricated, which shows a multiphase structure composed of face-centered cubic (FCC), L12 (ordered FCC), and Cr-rich body-centered cubic (BCC) phase by thermomechanical processing. Specifically, the aged sample displays the outstanding yield tensile strength (YTS, ∼1188 MPa), ultimate tensile strength (UTS, ∼1560 MPa) and work-hardening rate (WHR, ∼4.5 GPa) values as well as an acceptable plasticity of ∼16.6%. Theoretical calculations suggest that precipitation strengthening significantly contributes to achieving the fascinating tensile strength among various strengthening contributors. Further analyses reveal that multiple nanoscale stacking-fault (SF) networks are activated during plastic deformation in the aged alloy. Accordingly, the dual effects consisting of the hierarchical precipitation structure and SF networks lead to the combination of excellent tensile strength and strain-hardening capacity.

Mechanical properties and failure behavior of additively manufactured Al2O3 lattice structures infiltrated with phenol-formaldehyde resin

The lightweight design and load-bearing capacity of underwater vehicles remain perennial focal points. Ceramic lattice structures (CLSs) offer significant weight reduction while maximizing structural strength; however, their inherent brittleness poses a limitation. To optimize the performance of CLSs for underwater vehicle applications, a biomimetic Al2O3/phenol-formaldehyde (PF) resin composite structure (APCS) was proposed and fabricated by infiltrating additive-manufactured Al2O3 lattice structures (ALSs) with PF. Comprehensive assessments of the quasi-static mechanical properties were conducted using both experimental and simulation methods. The specific compressive strength and specific energy absorption of the APCSs under quasi-static compressive loading exhibited remarkable improvements, with the maximum values achieved from the body-centered cubic (BCC)/PF structure increasing by ∼15.23 and ∼307.93 times, respectively. In contrast to ALSs, the failure process of APCSs was gradual, with the confining pressure introduced by the PF promoting transverse crack propagation and layer-by-layer failure, thereby strengthening the ceramic lattice. Toughing mechanisms (i.e., crack arrest, crack deflection, and branching) were also observed in the APCSs. Furthermore, the simulation results aligned well with the experimental results, providing an in-depth analysis of internal damage and crack propagation. The improvements introduced by the composite structure in this study provide a reliable approach for obtaining lightweight and strong materials, thereby accelerating the application of ceramic-based materials in underwater vehicles.

Effect of rolling on the microstructure and mechanical properties of (FeCrNi)94Ti3Al3 medium entropy alloy fabricated via selective laser melting

The microstructure evolution and mechanical properties of the (FeCrNi)94Ti3Al3 medium entropy alloy, fabricated through selective laser melting, were investigated after warm-rolling. The as-built (FeCrNi)94Ti3Al3 alloy exhibited a heterogeneous microstructure with alternating coarse face-centered cubic (FCC) phase grains (∼20 μm) and fine body-centered cubic (BCC) phase grains (∼1 μm). However, after warm-rolling and subsequent recrystallization, the alloy transformed into a dual-phase equiaxed grains structure consisting of FCC and BCC phases with an average grain size of approximately 2.8 μm. Additionally, the previously banded distribution of the BCC phase changed to a random distribution. Notably, during the deformation process, a twinning-induced plasticity (TWIP) effect was observed in the warm-rolled and recrystallized (FeCrNi)94Ti3Al3 alloy, resulting in excellent ductility and a wide work-hardening platform.

Effect of Mixed Morphology (Simple Cubic, Face-Centered Cubic, and Body-Centered Cubic)-Based Electrodes on the Electric Double Layer Capacitance of Supercapacitors.

Supercapacitors store energy due to the formation of an electric double layer (EDL) at the interface of the electrodes and electrolyte. The present article deals with the finite element study of equilibrium electric double layer capacitance (EDLC) in the mixed morphology electrodes comprising all three fundamental crystal structures, simple cubic (SC), body-centered cubic (BCC), and face-centered cubic morphologies (FCC). Mesoporous-activated carbon forms the electrode in the supercapacitor with (C2H5)4NBF4/propylene carbonate organic electrolyte. Electrochemical interference is clearly demonstrated in the supercapacitors with the formation of the potential bands, as in the case of interference theory due to the increasing packing factor. The effects of electrode thickness varying from a wide range of 50 nm to 0.04 mm on specific EDLC have been discussed in detail. The interfacial geometry of the unit cell in contact with the electrolyte is the most important parameter determining the properties of the EDL. The critical thickness of the electrodes is 1.71 μm in all the morphologies. Polarization increases the interfacial potential and leads to EDL formation. The Stern layer specific capacitance is 167.6 μF cm-2 in all the morphologies. The maximum capacitance is in the decreasing order of interfacial geometry, as FCC > BCC > SC, dependent on the packing factor. The minimum transmittance in all the morphologies is 98.35%, with the constant figure of merit at higher electrode thickness having applications in the chip interconnects. The transient analysis shows that the interfacial current decreases with increasing polarization in the EDL. The capacitance also decreases with the increase of the scan rate.

Microstructure and mechanical property of CoCrFeNiAlxMn(1-x) dual-phase gradient high-entropy alloy coatings prepared by laser cladding

High-entropy alloy (HEAs), known for their balanced strength and ductility, are promising candidates for impact wear-resistant applications. In this study, CoCrFeNiAlxMn(1-x)(x = 0, 0.2, 0.8, 1.0) dual-phase gradient coatings with a layered structure were prepared using laser cladding technology to explore the microstructure evolution, tensile properties and fracture mechanism of gradient coating. As the Al content increased, the single-phase face-centered cubic (FCC) HEA coatings transitioned to dual-phase of FCC+ body-centered cubic (BCC) solid-solution, and finally to a single BCC phase. The remarkable improvement of microhardness is attributed to the dominance of the BCC phase and the impeding effect of the second phase particles on dislocation movement. The gradient coating exhibited a gradual change in internal element composition, microhardness, and structure along the depth direction, with the highest hardness value reaching 530 HV. Compared with the minimum tensile strength (69.03 MPa) and the minimum elongation (0.14 %) of single-layer coating, the gradient coatings exhibited a balance of high tensile strength and good plastic toughness, with a tensile strength of 597 MPa and an elongation of 4.08 %. Fracture analysis indicated a transition from ductile to brittle fracture in single-layer coatings as x values increased. The double-layer and four-layer gradient coatings displayed a mixed mode of brittle and plastic fracture. The study provides valuable insights into the design and fabrication of HEA gradient coatings, offering a novel approach to enhance the durability and performance of laser-clad coatings for various applications.

Microstructure and properties of WC-reinforced AlCoCrFeNiSi high entropy alloy coatings prepared via high-velocity arc spraying

In this research, (AlCoCrFeNiSi)100-x(WC)x (x=0, 20 and 40 wt%) high entropy alloy (HEA) coatings were successfully deposited on the surface of Q235 steel substrate using high-velocity arc spraying method. The study investigated the presence of WC particles on the phase composition, microstructure, tensile bonding strength, and corrosion behavior of the HEA coatings. X-ray diffraction analysis revealed that without WC particles, the predominant phase in the coating was a face-centered cubic (FCC). However, when 20 wt% and 40 wt% of WC particles were added, the phase composition shifted to include FCC, body-centered cubic (BCC), W3C, Cr7C3, and other carbides. The WC particles also reduced the crystalline grain size of the coatings from 14.75 nm to 10.34 nm. The microhardness value increased from 252.5 HV0.1 to a peak of 529.9 HV0.1, as the content of WC increased representing a microhardness improvement factor ranging from 1.4 to 3 times that of the substrate. The tensile bonding strength of the coatings was also enhanced with WC content. The coating with 40 wt% WC particles demonstrated the highest tensile bonding strength of 40.23 MPa. The cohesion, adhesion, and glue failures occurred after the tensile test, with adhesion failure being more prominent in the coatings without WC particles and glue failure being more prominent in the WC-reinforced coatings. Compared to the Q235 steel substrate, the coated samples showed enhanced resistance against corrosion due to the formation of the passive oxide layers. The effective resistance against corrosion was attained when the proportion of WC particles was 20 wt%, displaying the least values for corrosion current density and corrosion rate in 3.5 wt% NaCl solution. Examination through SEM and XPS analysis indicated that the coatings’ structures and the formation of protective passive layers enhanced the corrosion resistance.

Peculiar microstructure with high damping capacity for Al0.5CrFe2Ni medium-entropy alloy

In this paper, the effect of Al mole ratio on phase evolution, damping capacity and mechanical properties of the AlxCrFe2Ni (indicated by Alx, x = 0.3, 0.4, 0.5 and 0.7) medium-entropy alloys (MEAs) was investigated. The results show that the structure of the Alx MEAs changes from the face-centered cubic (FCC) phase dominated by the Al0.3 alloy to the body-centered cubic (BCC) phase dominated by the Al0.7 alloy. As the volume fraction of the BCC phase increases the corresponding grain size of the alloys decreases and then increases, which increases the ferromagnetic properties and decreases interfacial area in the Alx alloys. The high damping capacity of Al0.5 and Al0.7 alloys is corresponding to 0.05545, and 0.05044, respectively, under the synergistic effects of ferromagnetic damping and interfacial damping. The special honeycomb-like morphology of FCC phase distributed in the BCC matrix gives the Al0.5 alloy the highest damping capacity and yield strength.

First-principles calculation of the effect of V content on the properties of NbMoTaWVx refractory high-entropy alloys

This work focused on the influence of V content on NbMoTaWVx (x = 0.00, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75, 2.00) refractory high-entropy alloys (RHEAs). The influence of V content with structure stability, electronic properties, elastic properties, and thermodynamic properties was systematically studied by first-principles calculations and the Gibbs2 program. All alloys prefer to form body centered cubic (BCC) structure according to the minimum energy principle. The electronic properties show that the V element can strengthen the metallicity of NbMoTaWVx RHEAs. The results of elastic properties show that NbMoTaWV0.75 owns the highest ductility and lowest hardness at the same time. Moreover, according to the results of thermodynamic properties, the V element can reinforce the abilities of resistance for thermal softening and thermal expansion at high temperatures. This study can provide guidance for the design and practical preparation of RHEAs.

Achieved strength-plastic trade-off in HfMoNbTaTi refractory high-entropy alloy via powder metallurgy process

The practical application of refractory high-entropy alloys (RHEAs) has been limited by their brittleness at room temperature. This study prepared fine-grained HfMoNbTaTi refractory high-entropy alloys using a powder metallurgy process combining mechanical alloying (MA) and spark plasma sintering (SPS). This method effectively addresses the issue of room temperature brittleness and achieves a favorable balance between strength and plasticity. The resulting sintered alloy comprises two body-centered cubic (BCC) solid solution matrices and a range of nanoprecipitates, including the γ-phase, σ-phase, and α-phase. With increasing sintering temperature, the average grain size increased from 0.45 μm (at 1400 °C) to 4.56 μm (at 1700 °C). Simultaneously, the content of the γ-phase gradually decreases due to the greater influence of mixing entropy. Under quasi-static loading, the fine-grained multiphase structure not only benefits from grain boundary strengthening and precipitation strengthening effects, but also enhances the deformation uniformity, ultimately improving both the strength and plasticity. At 1450 °C, the sintered alloy exhibited a compressive yield strength of 2325 ± 8.40 MPa and a plastic strain of 26.44 ± 1.17 %. These values represent a 35.73 % increase in yield strength and a 120.33 % increase in plastic strain compared to those of the as-cast alloy. The deformation process at room temperature is mainly governed by the multiplication of screw dislocations and cross-slips. In the middle and late stages of deformation, the grains exhibit a preferred orientation, further enhancing the plastic strain. In summary, this study presents a practical approach for overcoming the issue of room temperature embrittlement in RHEAs.

Microstructural evolution, mechanical behavior, and deformation mechanisms of a lightweight Ti–Nb–Cr–V refractory high-entropy alloy at room and elevated temperatures

Refractory high-entropy alloys (RHEAs) have emerged as promising candidates for high-temperature applications owing to their distinctive mechanical properties. However, their limited tensile ductility and high density pose hurdles for further engineering utilization. In this study, we introduce a novel RHEA composition, Ti45Nb30Cr15V10 (at.%), distinguished by its reduced density (∼6.2 g/cm3), achieved through the assistance of CALPHAD (CALculation of PHAse Diagrams) modeling. The as-cast RHEA exhibits a single body-centered cubic (BCC) structure, demonstrating a tensile yield strength of ∼904 MPa along with a total elongation of ∼9.7 %. By employing cold rolling followed by recrystallized annealing (designated as the CRRA sample), we achieve notable enhancements in both strength and ductility. Specifically, the CRRA sample manifests an impressive tensile yield strength of ∼1010 MPa and a total elongation of ∼20.6 % at room temperature. Remarkably, even at an elevated temperature of 700 °C, the CRRA sample maintains notable strength, displaying a yield strength of ∼695 MPa. The observed dislocation behavior, transitioning from dual-system slip to multi-system slip, along with the intricate interactions of dislocation substructures (e.g., loops, tangles, networks, bands, and cells) and kink bands, are identified as the principal deformation mechanisms contributing to the exceptional tensile properties of the CRRA sample at room temperature. At 700 °C, the presence of wavy-slipping dislocations, induced by the strong pinning effect of component fluctuations, predominantly contributes to the strength of the CRRA sample. However, the emergence of Cr2(Ti, Nb, V) Laves phase at grain boundaries results in premature fracture. The extraordinary tensile properties exhibited by the CRRA sample at both room and elevated temperatures underscore its potential for advanced engineering applications.

Effect of B2 nanoprecipitates on mechanical behavior of TiZrNbVAl lightweight high entropy alloys upon dynamic loading

The addition of B2 nanoprecipitates provides a new way to improve the mechanical properties of lightweight high entropy alloys (LHEAs) with body-centered-cubic (BCC) structure. However, the study of B2 nanoprecipitates on BCC-LHEAs is limited to quasi-static tension. In this work, TiZrNbVAl LHEAs with BCC structure was chosen as model alloys and the effect of B2 nanoprecipitates on dynamic mechanical properties of TiZrNbVAl LHEAs was studied. The results show that the introduction of B2 nanoprecipitates not only significantly improves the dynamic strength, but also increases the plasticity from 31 % to more than 46 %, with an increase of more than 48 %. Microstructure evolution proves that during the plastic deformation process, the B2 nanoprecipitates promoted a large number of “second-generation bands” of dislocation in the separation of the first-generation bands, which effectively extended the plastic deformation region to the entire sample and improved the uniform deformation ability of LHEAs. Our results provide a solution for improving the mechanical properties of LHEAs under dynamic/impact conditions.

AlxHfTaTi (0≤x≤0.5) refractory medium entropy alloys with excellent room-temperature tensile properties

Refractory high entropy alloys are strong candidates for high-temperature structural materials, because of their high strength, excellent thermal stability and exceptional softening resistance under high-temperature. However, majority of the existing refractory high entropy alloys are seriously limited in widespread application, due to their severe brittleness at room temperature. In this study, we proposed a novel AlxHfTaTi body-centered cubic (BCC) refractory medium entropy alloy with remarkable strength-ductility combination at room temperature. Adjusting the atomic ratio of Al (from 0 to 0.5 at.%), we investigated the effect of Al on the structure-property characteristics of the alloy under as-cast as well as cold-rolled and annealed conditions. Compared with the as-cast samples, the rolled and annealed samples exhibit more excellent tensile properties due to the remarkable reduction of grain size resulted from recrystallization. The Al0.3HfTaTi sample annealed for 5 min exhibits outstanding comprehensive properties at room temperature, with a yield strength higher than 1000 MPa and a fracture elongation of up to 24 ± 1 %, respectively. Quasi in-situ EBSD analysis results reveal that, during tensile deformation, the grain size has a significant effect on the grain rotation and dislocation gliding. Small grains are more likely to initiate multiple slip bands, promoting the synergistic effect of grain rotation and dislocation gliding, thereby improving the ductility of the alloy. Our findings can provide new ideas for the development of refractory high entropy alloys with outstanding room-temperature tensile properties.

Identifying the in-situ origin of supercluster-induced ductile precipitates in Zr-based bulk metallic glasses

A sandwich architecture including double crystal substrates and a single glass-forming droplet has been successfully designed based on the simplified liquid-bridge methods in multicomponent alloys. The multiscale precipitates mainly consisting of β-phase dendrites with a body-centered cubic (BCC) structure, cubic CuZr2 phase, and icosahedral quasicrystalline phase (I-phase) could be simultaneously identified in dissimilar regions of the glass-forming matrix during heat-induced dissolution or diffusion from crystal substrate to glass-forming droplet. The gradient distributions of crystal-like clusters not only accelerate diffusion velocity due to the collective atomic motion but also can simultaneously modulate the atomic-scale structure, mechanical response, and chemical composition via tracing a high-throughput strategy. The present work provides new insights to discover the formation mechanism of the representative microstructures strongly associated with the atomic-scale structure-property-composition relationships and is also helpful to shed light on the in-situ origin or structural mechanism of supercluster-induced multiscale precipitates in developing bulk metallic glasses (BMGs) and in-situ formed BMG composites (BMGCs).

The extended scaling laws of the mechanical properties of additively manufactured body-centered cubic lattice structures under large compressive strains

Additively manufactured lattice structures are porous light-weight structures with mechanical properties that are dictated both from the topology and the parent material properties. When printed from metals, these structures can withstand large continuous plastic deformation. In this paper, we focus on body-centered cubic (BCC) lattice structures under compression up to large deformation strains, and we propose relations between the slenderness ratio of struts and the following mechanical properties: Young's modulus, yield strength, hardening rate of the structure and the densification strain. We perform a systematic study using finite element modelling (FEM) to find how both material properties and lattice structures are affecting the effective mechanical properties of BCC lattice structures under compression. Based on this analysis we propose the scaling laws of the mechanical properties. The scaling laws can be explained as an extension of the Gibson-Ashby power law relations for bend-dominated structures with non-slender beams. We also discuss how rounding the connections between the struts using fillets affects the scaling laws. We demonstrate the scaling laws in the analysis of experimental results, showing the accuracy and limitations of the scaling laws in predicting the mechanical properties, with an emphasis on large deformations. In the analysis, we use experimental values published in literature, and we also present here experimental results of lattice structures printed from Inconel 718.

Sulfuric acid leaching of ferronickel and preparation of precursor materials for power batteries: Strategy of enhanced leaching through thermal activation and its mechanism

With the development of the new energy industry, the demand for iron phosphate and nickel–cobalt hydroxide precursor materials in the power battery industry has increased sharply. Ferronickel with low content of other impurities, derived from electric furnace smelting of laterite nickel ore, contains iron, nickel, and cobalt components used for the production of two kinds of power batteries. In this study, the sulfuric acid leaching behaviors of the water quenched ferronickel particles under atmospheric pressure was investigated. Practically, the direct leaching performance of these ferronickel particles in sulfuric acid is unsatisfactory. The leaching of Ni, Co and Fe was only 4.52 %, 3.58 % and 3.83 %, respectively, at the initial acid concentration of 3 mol/L, liquid–solid ratio of 12 mL/g, leaching temperature of 95 °C and time of 4 h. However, through thermal activation, the face-centered cubic (FCC) Fe-Ni phase was transformed into the body-centered cubic (BCC) structure, which significantly improved its acidic leaching activity. Under the thermal activation at 800 °C for 2 h, the leaching of Ni, Co and Fe reached 91.27 %, 90.12 % and 89.19 %, respectively, at the same leaching conditions. After oxidizing the Fe(II) in lixivium to Fe(III) using hydrogen peroxide, 89.3 % of Fe was selectively precipitated into battery-grade iron phosphate by adding phosphoric acid and coordinating solution pH. Nickel and cobalt in residual solution was then recovered to nickel–cobalt hydroxide by precipitation after removing impurity ions in advance. This study provides a new pathway for the value-added utilization of ferronickel in the power battery industry, not only in the production of stainless steel.

Impact of copper and manganese on phase transformation, microstructural development and material strength in CoCrFeNi high-entropy alloys through mechanical alloying

CoCrFeNiX (X = Cu, Mn) equiatomic high-entropy alloys (HEAs) were prepared through mechanical alloying (MA) followed by sintering at moderate temperature. The prepared HEAs were subjected to X-ray diffraction and microscope techniques to evaluate their phase evolution, microstructure, and elemental composition. Alloyed CoCrFeNiCu powder consists of two face centered cubic (FCC) phases (FCC1 and FCC2), whereas, CoCrFeNiMn powder showed a major FCC phase with a minor body centered cubic (BCC) phase. After sintering, bulk CoCrFeNiMn alloy showed only a single solid solution FCC phase, and the bulk CoCrFeNiCu still contained dual FCC phases. The elemental composition analysis revealed that both HEAs are equiatomic in composition. The average microhardness of CoCrFeNiCu and CoCrFeNiMn HEAs was 85 ± 15 HV and 147 ± 20 HV, respectively. It was observed that the presence of Cu in CoCrFeNiCu reduces the hardness of the HEA due to segregation. This study demonstrates the influence of the fifth metal on the phase evolution, microstructure, and mechanical properties of the HEAs.