Spark Plasma Sintering Research Articles

Densification behavior of ultrafine WC‐based composites with AlxCoCrCuFeNi high‐entropy alloy binders

AbstractUltrafine WC‐based cemented carbides with 10 wt.%AlxCoCrCuFeNi high‐entropy alloy (HEA) binders were fabricated by spark plasma sintering, and the effects of HEA binders on the densification behavior of the WC‐HEA cemented carbides were studied. The densification of the WC‐HEA cemented carbide, as well as traditional WC‐Co, can be divided into the slow densification stage, rapid densification stage, and final densification stage. The densification behavior of the WC‐HEA cemented carbides largely depends on the performance of the HEA binder during the SPS process. The sluggish diffusion effect of HEA weakens the diffusion of W atom on the powder particle surface and inhibits the growth of WC grain. Consequently, the disappearance of pores in the sintered compact is hindered, which leads to a low relative density of the WC‐HEA cemented carbide. With the increase of Al content, the inhibitory effect of the AlxCoCrCuFeNi binder on the growth of WC grain is suppressed, and an Al‐containing phase with a low melting point is more likely to form. Therefore, the relative density of the WC‐10 wt.%AlxCoCrCuFeNi cemented carbide raises linearly with increasing Al content of the HEA binder.

Activation and development of direct plasma spark sintering and this method after the synthesis of combustion of ceramic-metal compositions through different mixtures of metal melts and/or intermetallic compounds

The article shows the effect of different mixtures melts of metals and/or intermetallic compounds with various oxide, non-oxide additives, obtained solid solutions of metallic phases during spark plasma sintering, spark plasma sintering after combustion synthesis on the phase composition, micrstructure, grains sizes of crystalline phases, relative density, linear shrinkage, microstructural featres of boundary layers, paths of microcracks, physical-mechanical properties, values of standart erors of properties of samples. Synthesized powders of h-BN, B4C, NiTi, NiZr are characterisized by high intensity of crystallization of h-BN, B4C, NiTi, NiZr. Sintered by spark plasma method c-ZrO2, c-BC2N at pressing loadings 35 MPa and 1400 oC, 5 GPa and 2327 oC in boron melt show evoluted crystalli-zation of c-ZrO2, с-BC2N phases, respectively, crystalline, uniform and dense microstructures. Obtained by combustion synthesis powder shows multi-phase composition with various crystallization of phases. Sintered by direct spark plasma method samples show evoluted mullitization, crystallization of c-ZrO2, solid solutions of metallic phases, but in the samples, obtained by spark plasma method in different sintering conditions after combustion synthesis are visible crystalline, multi-intensive phases. The samples show crystalline, multi-uniform and multi-dense microstructures, variously dispersed grains of crystalline phases. Sintered samples are differ by the relative density, linear shrikage, density, uniformity, width, path of boundary layers and propagating microcracks across these boundary layers, the resistance to the cracking, values of physical-mechanical properties, values of standart errors of properties of samples.

Combustion synthesis and spark plasma sintering processing of (1‐x)Ba(Zr₀.₂Ti₀.₈)O₃‐x(Ba₀.₇Ca₀.₃)TiO₃ ceramics

AbstractSolution combustion synthesis (SCS) has proven to be one of the simplest and fastest methods, using inexpensive materials and resulting in homogeneous stoichiometry with nanometric particle sizes. The spark plasma sintering (SPS) method has been used to obtain high‐density ceramic materials with excellent control of microstructure. This work reports the successful combination of these two techniques for the fabrication of the high‐density lead‐free ferroelectric system (1‐x)Ba(Zr₀.₂Ti₀.₈)O₃‐x(Ba₀.₇Ca₀.₃)TiO₃. The X‐ray diffraction of the powder indicates the majority formation of the perovskite structure and other residual reaction products, indicating a reactive powder. The SPS method resulted in highly densified samples, reaching relative density values close to 99% with a single‐phase perovskite structure. Rietveld refinement revealed the presence of at least two perovskite phases, independent of calcium concentration. Dielectric measurements showed anomalies in both the real and imaginary parts of the dielectric permittivity, which are typical of phase transitions and a low dielectric loss for all compositions. This study shows that the combined use of SCS and SPS technique can be a powerful protocol to produce dense, fine‐grained lead‐free ferroelectric ceramics at relatively low temperatures and in short time periods.

Reflectance spectral studies of spark plasma sintered tungsten carbide pellet

Abstract We report the first spectral reflectance of tungsten carbide (WC) as potential solar selective absorber. We developed an optical measurement system for visible to mid-infrared spectroscopy, covering the range of 0.1 to 2.5 eV, to evaluate the solar selectivity. A polycrystalline WC was prepared using spark plasma sintering method. The measured spectral reflectance of WC exhibits a low-energy plasma excitation around 0.6 eV corresponding to the cutoff energy of sunlight, consistent with ab initio calculations, thus making it preferable for the solar selective absorber. We also discuss effects of the sample quality on the spectral reflectance.

Effect of different sintering process on mechanical properties and microstructure of TiB2‐TiN‐based cermet material

AbstractTiB2‐TiN‐NiTi cermet material was prepared by spark plasma sintering technology (SPS). The effects of the sintering process on their relative density, mechanical properties, and microstructure were studied with 74TiB2‐20TiN‐6NiTi as the composition system. The results showed that TiB2‐TiN‐based cermet material with the best mechanical properties was prepared under the sintering temperature of 1650°C and the holding time of 5 min. The relative density, flexural strength, fracture toughness, and hardness are 97.7%, 762.7 MPa, 5.5 MPa·m1/2, and 18.47 GPa, respectively. However, if the holding time keeps for 3 min under the sintering temperature of 900°C and then 5 min under the sintering temperature of 1650°C, the relative density, flexural strength, fracture toughness, and hardness of TiB2‐TiN‐based cermet reach 99.1%, 931.3 MPa, 5.8 MPa·m1/2, and 19.15 GPa, respectively. In comparison, they have been greatly improved by 1.4%, 22.1%, 5.5%, and 3.7%, respectively. The final holding time can also affect the mechanical properties of TiB2‐TiN‐based cermet material. When it is higher than 5 min, it will cause irregular growth and abnormal growth of grains, which can decrease the flexural strength of TiB2‐TiN‐based cermet material.

Mechanical characteristics of dual‐phase medium‐entropy boride/carbide ceramics synthesized through SPS

AbstractMaterial scientists constantly look for new compounds with exceptional properties to meet the ever‐changing technology and industry needs. Hereby, the dual‐phase medium‐entropy ceramics have fabricated by employing high‐energy ball milling (HEBM) and spark plasma sintering (SPS) techniques on commercial boride and carbide powders of IVB group metals. The boride and carbide powders have undergone 3‐hour milling in a planetary ball mill, followed by SPS processing at 1800°C and 2000°C under 30 MPa uniaxial pressure for 10 min. The milled powders and SPS'ed ceramics have been characterized, focusing on composition, density, and microstructure using X‐ray diffractometry (XRD) and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS). Microhardness and sliding wear tests have also been performed on the SPS'ed ceramics. The systematic analysis of the characterization results has revealed that the microstructural evolution and mechanical properties of the dual‐phase ceramics have developed to a comparable level with the single‐phase ceramics, regardless of the sintering temperature. In fact, the dual‐phase ceramics sintered at 1800°C come to the forefront due to the superior hardness and fracture toughness values (∼ 16 GPa and ∼ 5.4 MPa.m1/2).

Mechanical Properties of Cu70Fe30 (at%) Bulk Metastable Alloys Prepared by Mechanical Alloying and Spark Plasma Sintering

The equilibrium‐insoluble Cu and Fe metals with a composition of Cu70Fe30 (at%) are mechanically milled for 20 h, resulting in a metastable single‐phase face‐centered cubic supersaturated solid solution (γS). The alloy powders are consolidated by spark plasma sintering (SPS) at 0.6Tm (622 °C) and 0.7Tm (772 °C), where Tm is the melting point of Cu70Fe30 (1219 °C). Scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and electron backscatter (EBSD) analyses are performed on mechanically alloyed powders and SPS bulk samples. Compressive stress–strain and hardness tests are also conducted on the bulk SPS samples to evaluate the mechanical properties. The metallographic study reveals that the γS phase decomposes into Cu‐rich γ and Fe‐rich α phases after SPS. The 0.6Tm sample exhibits a continuous γ‐network phase surrounding an ultrafine γ + α mixture, causing brittle behavior due to crack propagation during compressive testing. In contrast, the 0.7Tm sample features a discontinuous γ‐network phase, enhancing ductility and resulting in a bimodal grain structure. This sample demonstrates superior mechanical properties, combining excellent strength (1056 MPa) and ductility (23%) due to the coexistence of coarser γ‐network grains (1–2 μm) and ultrafine γ + α grains (200–500 nm).

A novel method for strengthening C/C composite joint with high entropy alloy/Ni composite interlayers by spark plasma sintering: In-situ synthesis of high entropy cermet joint structure

C/C composite was successfully brazed with TiZrHfTa/Ni or ZrHfNbTa/Ni composite interlayers using spark plasma sintering. The influence of different interlayers and joining parameters on the joint morphology, shear strength at room temperature and 1000 °C was investigated. For both composite interlayers, the C/C joints obtained at 1800 °C for 30 min consisted of a single high entropy cermet structure, with a near equimolar high entropy carbide hard phase and a near pure Ni binder phase. However, the use of different composite interlayers resulted in differences in the elastic modulus and hardness of the formed high entropy carbide phase. The maximum shear strengths of the obtained C/C composite joints using TiZrHfTa/Ni and ZrHfNbTa/Ni interlayers at room temperature were close, with value of 37.49 ± 1.44 MPa and 38.95 ± 1.26 MPa, respectively. Because (Zr-Hf-Nb-Ta)C had better high-temperature stability than (Ti-Zr-Hf-Ta)C, the obtained C/C-ZrHfNbTa/Ni-C/C joint exhibited a higher shear strength of 28.54 ± 1.71 MPa at 1000 °C. After shear testing at both room temperature and 1000 °C, fractures in all joints predominantly occurred within the C/C composite near the reaction layer, indicating a substrate failure mode. The use of composite interlayers resulted in C/C composite joints with excellent shear strength, primarily due to the in-situ synthesized high entropy cermet reaction layer, which provided superior strength and toughness. Additionally, the laser-textured pattern on the C/C composite surface formed numerous interlocking structures at the joint interface, further enhancing the joints' shear strength.

Pressureless synthesis and consolidation of the entropy-stabilized (Hf0.25Zr0.25Ti0.25V0.25)B2-B4C composite by ultra-fast high-temperature sintering (UHS)

Entropy-stabilized Ultra High-Temperature Ceramics (UHTC) offer a groundbreaking solution to the challenges of extreme environments, showcasing enhanced mechanical properties, thermal stability, and resistance to oxidation at high temperatures. The consolidation of UHTC by ultra-fast high-temperature sintering (UHS) significantly reduces processing times and temperature and can produce dense high-performance ceramics with superior mechanical properties. This study reports the pressureless synthesis and consolidation of the entropy-stabilized (Hf0.25Zr0.25Ti0.25V0.25)B2-B4C composite through UHS within 1minute, starting from transition metal diboride powders. B4C acts as an effective sintering aid, promoting the densification of the system and the formation of a nearly single-phase hexagonal diboride with a diboride-eutectic phase. Furthermore, a secondary minor hexagonal phase rich in V and Zr is formed close to the eutectic regions. Sintering currents of 40A were necessary to reach densities higher than 90% under pressureless conditions, achieving nano hardness higher than 27.3GPa, comparable with high-entropy diborides produced by Spark Plasma Sintering. The study highlights the entropy-stabilized phase formation, diffusion, densification, and grain mechanisms involved during UHS. The work contributes to understanding entropy-stabilized ceramics produced by UHS as a faster and less energy-consuming process than more conventional sintering methods.

Microstructural characteristics, electrical conductivity and mechanical properties of Cu matrix composites reinforced with dual-phase borides

The effect of boride content on the microstructure, electrical conductivity, and mechanical properties of TiB2-MB2/Cu composites (M=Cr, Mo, and Zr) was systematically investigated. The composites were prepared via spark plasma sintering. The results indicated that the double borides were uniformly distributed in the Cu matrix without visible agglomeration, and excellent interfacial bonding was achieved between the borides and the Cu matrix. The electrical conductivity of the Cu composite with 5 wt.% TiB2 and 15 wt.% ZrB2 increased by 503 % compared to the Cu-20 wt.% TiB2 composite. However, the hardness of the Cu composite with 5 wt.% TiB2 and 15 wt.% ZrB2 decreased by only 22 %. The wear resistance of the composites was significantly enhanced due to the synergistic effect of the dual-phase boride particles. The wear resistance of the Cu composite with 5 wt.% TiB2 and 15 wt.% ZrB2 was 4.12 times higher than that of the Cu-20 wt.% TiB2 composite standard sample when tested under an applied load of 10 N. The worn surface of the composites exhibited minimal roughness. Therefore, the Cu matrix composites with dual-phase borides achieved desirable comprehensive performance in terms of electrical, mechanical, and tribological properties.

Investigation of the Effect of Temperature on the Microstructural and Mechanical Properties of the Ultra-High Temperature Ceramic Composite ZrB2-SiC-TiC Using the Multi-Step Spark Plasma Sintering Method

Investigation of the Effect of Temperature on the Microstructural and Mechanical Properties of the Ultra-High Temperature Ceramic Composite ZrB2-SiC-TiC Using the Multi-Step Spark Plasma Sintering Method

Scintillation properties of SrCl2:Eu transparent ceramics fabricated by spark plasma sintering method

Scintillation properties of SrCl2:Eu transparent ceramics fabricated by spark plasma sintering method

Investigation of wear and transverse rupture strength of AA2219/ZrO2/B4C hybrid composite materials prepared with 3D ball mixer and produced by spark plasma sintering

ABSTRACT Aluminum alloys have advanced to meet the growing demand for strong, lightweight materials. The 2219 aluminum alloy has gained popularity due to its superior mechanical properties and high copper content. However, despite these improvements, the wear characteristics of metal matrix composites with ceramic reinforcements have been suboptimal. This study aims to develop metal matrix composites that improve the mechanical and wear properties of AA2219 aluminum alloy. A homogeneous mixture was created using a 3D mechanical mixer/miller apparatus. ZrO2 and B4C reinforcements were added to the matrix in ratios of 5%, 10%, and 15%, including hybrid composites with both reinforcements. Mechanical and wear characteristics were analyzed, and a 3D profilometer was used to evaluate wear properties and determine tribological parameters. The results showed that the pulverized reinforcement particles were uniformly dispersed within the matrix. The sample with a hybrid reinforcement comprising 15% of the total composition exhibited the highest hardness, measuring 164.96 hV. This study demonstrates that incorporating ceramic reinforcements in specific ratios can significantly enhance the mechanical and wear properties of 2219 aluminum alloy composites.

Optimizing the mechanical properties of Al4SiC4 ceramics: A study on incorporating Y2O3 and spark plasma sintering

The present study focuses on optimizing the mechanical properties of Al4SiC4 ceramics by incorporating Y2O3 additives and utilizing spark plasma sintering. A native oxide layer, predominantly composed of Al2O3 with trace amounts of SiO2, was detected on the surface of the Al4SiC4 powder. Following sintering at 1823 K, Al4SiC4 was identified as the dominant phase, with Y3Al5O12 (YAG) recognized as the secondary phase. The effects of YAG on grain growth in Al4SiC4 is clarified based on experimental findings and molecular dynamics simulations. Additionally, the presence of SiO2 within the native oxide layer of Al4SiC4 is examined from both microstructural and thermodynamic perspectives. Precise optimization of the Y2O3 content is essential for enhancing mechanical properties, with an optimal content of 3 wt% yielding maximum values of flexural strength and fracture toughness at 436 MPa and 4.0 MPa·m1/2, respectively, along with Vickers hardness values of 12.0 GPa.

Improving thermoelectric properties of CuMnSb alloys via strategic alloying with magnetic MnSb and Cu

MnSb alloys are promising candidates for thermally stable magnetic materials in spintronic devices due to their high Curie temperature. When alloyed with transition metals, they hold potential as thermoelectric materials by adopting a half-Heusler structure. Among the few 3d transition metal-based compounds, CuMnSb alloys exhibit antiferromagnetic properties along with thermoelectric behavior. In this study, the CuMnSb alloy was synthesized using arc-melting, followed by powdering and spark plasma sintering. The thermoelectric properties were characterized in a temperature range of 298–673 K. The results indicate a significant improvement in the thermoelectric figure-of-merit (zT) of CuMnSb compared to MnSb, attributed to the increased power factor and reduced thermal conductivity through Cu alloying. These findings demonstrate the potential for obtaining half-Heusler-like thermoelectric materials by tailoring high-temperature magnetic materials.

Boosting the Mechanical and Thermal Properties of CUG-1A Lunar Regolith Simulant by Spark Plasma Sintering

The mechanical and thermal properties of the fabricated structures composed of lunar regolith are of great interest due to the urgent demand for in situ construction and manufacturing on the Moon for sustainable human habitation. This work demonstrates the great enhancement of the mechanical and thermal properties of CUG-1A lunar regolith simulant samples using spark plasma sintering (SPS). The morphology, chemical composition, structure, mechanical and thermal properties of the molten and SPSed samples were investigated. The sintering temperature significantly influenced the microstructure and macroscopic properties of these samples. The highest density (~99.7%), highest thermal conductivity (2.65 W·m−1·K−1 at 1073 K), and the best mechanical properties (compressive strength: 370.2 MPa, flexural strength: 81.4 MPa) were observed for the SPSed sample sintered at 1273 K. The enhanced thermal and mechanical properties of these lunar regolith simulant samples are attributed to the compact structure and the tight bonding between particles via homogenous glass.

Microstructure, Mechanical, and Tribological Properties of SiC-AlN-TiB2 Multiphase Ceramics

SiC multiphase ceramics were prepared via spark plasma sintering using AlN and TiB2 as the second phase and Y2O3 as a sintering additive. The effects of TiB2 content (10 vol.% and 20 vol.%) and sintering temperature (1900 °C to 2100 °C) on the phase composition, microstructure, and mechanical and tribological properties of SiC multiphase ceramics were investigated. The results showed that Y2O3 reacts with Al2O3 on the surface of AlN to form the intercrystalline phase Y4Al2O9 (YAM), which promotes the densification of the multiphase ceramics. The highest density of SiC multiphase ceramics was achieved at 10 vol.% TiB2 content. Moreover, TiB2 and SiC exhibited good interfacial compatibility. In turn, a thin solid-solution layer (~50 nm) was formed by SiC and AlN at the interface. The periodic structure of SiC prevented the dislocation movement and inhibited the base plane slip. The most optimal mechanic characteristics (a density of 98.3%, hardness of 28 GPa, fracture toughness of 5.7 MPa·m1/2, and bending strength of 553 MPa) were attained at the TiB2 content of 10 vol.%. The specific wear rates of SiC multiphase ceramics were (4–8) × 10−5 mm3/N·m at 25 °C and 2.5 × 10−5 mm3/N·m at 600 °C. The wear mechanism changed from abrasion at 25 °C to a tribo-chemical reaction at 600 °C. Therefore, adding lubricious oxides of TiB2 is beneficial for the improvement in wear resistance of SiC ceramics at 600 °C.

Microstructure Evolution and Mechanical Behavior of TiB-Reinforced Ti-6.5Al-2Zr-1Mo-1V Matrix Composites Obtained by Vacuum Arc Melting and Spark Plasma Sintering

Ti-6.5Al-2Zr-1Mo-1V/TiB metal matrix composites with 3 wt.% of TiB2 were obtained using vacuum arc melting and spark plasma sintering methods and compared with an unreinforced Ti-6.5Al-2Zr-1Mo-1V alloy. The microstructures of the unreinforced Ti6.5Al-2Zr-1Mo-1V alloy in the as-cast and as-sintered conditions were quite typical and consisted of colonies of α-lamellae embedded in the β matrix. The microstructure of the as-cast Ti-6.5Al-2Zr-1Mo-1V/TiB composite composed of TiB fibers randomly distributed within the two-phase α/β matrix, while the as-sintered composite had a network-like microstructure, in which areas of the two-phase α/β matrix were delineated by walls of TiB fibers. At room temperature, the yield strength of the as-cast and as-sintered Ti-6.5Al-2Zr-1Mo-1V alloy were 800 and 915 MPa, respectively, with a plasticity of 18% in both conditions. The addition of TiB fibers contributed to a ~40 and 50% strength increment, with values of 1100 and 1370 MPa for the as-cast and as-sintered composites, respectively. In the as-sintered composite, the strengthening effect reduced at 400 °C and almost disappeared at elevated temperatures of 800–950 °C. The as-cast composite showed much higher strength during warm and hot deformation—at 800–950 °C, the yield strength of the as-cast composite was 50% higher compared to the Ti-6.5Al-2Zr-1Mo-1V unreinforced alloy. A higher rate and degree of globularization were established for the as-cast composite compared to the unreinforced alloy. For the as-sintered composite, a noticeably lower rate and degree of globularization was shown. During hot compression of the as-cast composite, TiB fibers reoriented towards the metal flow direction, while the network microstructure formed in the as-sintered composite transformed into clusters of borides unevenly distributed within the matrix. Based on the obtained results, the apparent activation energy of plastic deformation was calculated, and the operating deformation mechanisms were discussed both for the as-cast and as-sintered composites. The Arrhenius flow stress model and the dynamic material model were used to evaluate the deformation behavior of composites beyond the experimentally studied temperatures and strain rates.

Tribological Properties of SPS Reactive Sintered Al/MoS2 Composites

In search of opportunities to improve mechanical properties and abrasion resistance, composites based on aluminum reinforced with MoS2 particles were produced. The authors’ previous research indicated the possibility of obtaining hard dispersion precipitates of the Al12Mo intermetallic phase as a result of the reaction of the composite components at a temperature exceeding 550 °C during the SPS (Spark Plasma Sintering) process. This work focused on optimizing the SPS consolidation process and assessing the microstructure and mechanical properties of the obtained materials. A series of experiments proved that by increasing the amount of the strengthening phase and increasing the process temperature, a significant amount of Al12Mo and Al5Mo strengthening phases is produced. Exceptionally good dispersion of reinforcing particles and the presence of layered MoS2 crystals, while ensuring optimal parameters of the synthesis process, lead to a change in friction mechanisms and improved abrasion resistance through an approximately 30-fold decrease in the wear factor.

Correlation of microstructure, mechanical properties and electrical conductivity of Fe-Cu alloys produced by high-energy 3D ball milling and spark plasma sintering

ABSTRACT Fe-Cu is known as a metastable and immiscible alloy. Therefore, many problems are encountered in the production of Fe-Cu alloys by conventional casting. Researchers have used different techniques for the production of successful Fe-Cu alloys. For this reason, in this experimental study, the production of pure Fe and Fe-Cu (10%, 20% and 50% by volume) alloy compacts was investigated by spark plasma sintering, a powder metallurgy technique. The effects of Cu addition at different volume ratios on microstructure, density, hardness, three-point bending, wear and electrical conductivity were investigated. It has been determined that the microstructures in Fe-Cu alloys consist of α-Fe and ϵ-Cu phases. Compared to the pure-Fe sample, improvements were determined in the density, mechanical properties and electrical conductivity of the Fe-Cu alloy samples produced with the addition of Cu at 10%, 20% and 50% volume ratios. When the Fe-Cu alloys were compared with each other, the highest density, hardness, bending stress at break and the lowest wear rate were determined in the Fe-Cu alloy containing 20% ⁣⁣volume ratio Cu. The addition of Cu to Fe at 50% volume ratio caused a decrease in the density, mechanical properties and electrical conductivity.