Spark Plasma Sintering Technique Research Articles

Microstructure and mechanical properties of in-situ Ti5Si3/TC4 composites via spark plasma sintering and hot rolling

In this study, low energy ball milling and spark plasma sintering techniques prepared the in-situ synthesized Ti5Si3 reinforced Ti-6Al-4V (TC4) matrix composites and then rolled them at high temperatures. In the composites with high Si content, the Ti5Si3 particles distributed at the interface of α-phase and β-phase agglomerated and then formed a quasi-continuous network structure, which will deteriorate the plasticity of the composites. After hot rolling, the grains of the composite were significantly refined, and more Ti5Si3 particles were precipitated. With the increase in Si content, the tensile strength of sintered composites increased slightly, but the elongation decreased greatly. After hot rolling, the tensile strength of the composite increased significantly with an increment of 359.4 MPa, among which the composite with 0.6 wt% Si achieved a synchronous increase in strength and plasticity. The strengthening mechanism of sintered composites included dislocation strengthening, solution strengthening, and grain refinement, among which dislocation strengthening and grain refinement were the main strengthening mechanisms. The strengthening mechanism of rolled composites was mainly the dislocation strengthening caused by rolling, the grain refinement, and the mismatch of thermal expansion coefficient.

Liquid lithium wettability studies on novel zirconium-alloyed porous tungsten

Liquid lithium wettability has been investigated on novel zirconium-alloyed porous tungsten fabricated by the place-holder spark plasma sintering technique. This paper investigates the wetting properties of liquid lithium on the substrates by in vacuo contact angle measurements of lithium droplets at Penn State’s IGNIS-2 facility. X-ray Photoelectron Spectroscopy analysis was performed on the samples to investigate the role of the surface chemistry in the contact angle behavior of lithium on the substrates. It was seen that hydrated and hydroxylated states of the surface play a key role in affecting the lithium affinity of the surface.

Microstructure and Physical Properties of Nonmagnesium and Magnesium-Based High-Entropy Alloys: A Comparison Study

Abstract In this investigation, (Ti-Mo-Zr)60Co20Cr20, (Ti-Mo-Zr)60Al30Si10 (non-magnesium-based), and (Ti-Mo-Zr)60Cu10Mg30 (magnesium-based) high-entropy alloy (HEA) samples are prepared via mechanical milling and then by spark plasma sintering technique. The microstructure morphology is examined using x-ray diffraction and scanning electron microscopy with energy-dispersive x-ray spectroscopy. The microstructure reveals that there would be a strong correlation between phase structure and sustainability for localized corrosion behavior. The lowest crystallite size of the magnesium-based HEA powder mixture suggests the highest corrosion resistance because of the solid-solution face-centered cubic and body-centered cubic phases for 20 h of milling. The correlation between the microstructural morphology and functional properties such as hardness, corrosion resistance, and potentiodynamic parameters are compared for both magnesium-based and non-magnesium-based HEAs and analyzed to elucidate their suitability for lightweight vehicle applications.

Interfacial Evolution of WC-Co/AISI 304L Diffusion Bonded Joint Obtained by Flash SPS Technique

Interfacial Evolution of WC-Co/AISI 304L Diffusion Bonded Joint Obtained by Flash SPS Technique

Effect of sintering parameters on phase evolution, microstructural development and mechanical behavior of Ni46Al12Co18Cr8Fe12Mo4 high entropy alloy synthesized via mechanical alloying and spark plasma sintering

The aim of this research work was to study phase evolution, microstructural development and resulting mechanical properties in Ni46Al12Co18Cr8Fe12Mo4, at. % high entropy alloys (HEAs) synthesized via spark plasma sintering (SPS) of 50 hr mechanically alloyed (MAed) powder with varied sintering parameters. Detailed microstructural analysis of the consolidated samples revealed that sintering at 1100 °C resulted in improved densification, i.e. up to 99% and enhanced grain growth compared to the samples sintered at lower temperatures. Phase analysis of the sintered HEAs envisaged formation of face centered cubic (FCC) structured single-phase solid solution with minor amount of brittle sigma (σ) phases. Phase diagram generated from Thermo-Calc shows that volume fraction of the σ phases decreases continuously with temperature and further they dissolve at 1180 °C, which is in close agreement with experimental results of differential thermal analysis (DTA) performed on the sintered samples. Moreover, microhardness of the consolidated HEAs decreased gradually with increase in sintering temperature, ascribed to lower volume fraction of the brittle σ phases at higher temperature. Further, nanoindentation test was conducted to estimate the hardness of the individual phases and it was found that nanohardness of σ phase is approximately 1.7 times higher than that of the solid solution phase. The HEA sintered at 1100 °C showed an excellent strength-ductility synergy, with a compressive yield strength of 1121 ± 21 MPa and the elongation to failure up to 20 ± 1%, attributed to the presence of ductile FCC phase with minor amount of brittle σ phase. The present study demonstrates the potential of SPS technique to synthesize Ni base HEA with excellent thermal stability and superior mechanical properties for structural applications.

Phase prediction, densification, and microstructure of AlCrFeNi(TiO2)x high entropy alloy composite fabricated by spark plasma sintering

This study incorporates the knowledge of empirical calculation and computational concepts using Thermo-Calc as a design guide to develop AlCrFeNi high entropy alloy (HEA). Subsequently, a novel AlCrFeNi HEA composite consisting of varying weight percentages (wt%) of TiO2 reinforcements is synthesized using mechanical alloying (MA) and spark plasma sintering (SPS) techniques. Our work investigated the role of TiO2 reinforcement on the densification behavior, phase changes, microstructure, and properties of AlCrFeNi HEA. The phase diagram was constructed using Thermo-Calc software. Powder densification during SPS was analyzed using obtained sintering data. The samples were characterized using Xray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The density and micro-hardness were evaluated. The result shows that the densification during SPS is dependent on kinetic mechanisms such as melt diffusion, surface diffusion, and plastic flow. Phases of the disordered BCC phase (rich in FeCr) and ordered B2 phase (rich in NiAl) were found in the AlCrFeNi HEA. The phases were consistent with the prediction using thermo-calc software. The BCC phases in the AlCrFeNi are retained regardless of the addition of TiO2 particles but with the diffusion of Ti with O atoms fitting into the interstitial sites in the BCC and B2 lattice. The microstructure verified the homogeneous distribution of the TiO2-rich phase within the BCC and B2 phases of the AlCrFeNi HEAs. The density decreases with the adding TiO2. The hardness of reinforced AlCrFeNi is enhanced from 537.24 Hv to 752.74 Hv with an increment of TiO2 reinforcement from 0 to 8 wt%. TiO2 particles acted as impediments to the mobility of dislocation, thereby increasing the resistance to deformation of HEA composites during micro indentation.

Influence of laser texturing on interfacial bonding strength of W/Cu joint by spark plasma sintering

In this study, a spark plasma sintering(SPS) technique is used to bond tungsten(W) and copper(Cu) based on the laser texturing tungsten surface. Five microstructures, namely pristine structure, micropores1, micropores2, microgrooves, and nanoripples, were fabricated on the tungsten surface, and the effect of the microstructures on the shear properties, thermal shock resistance, and thermal conductivity of the tungsten/copper joints was investigated. W with the original planar morphology did not form an effective connection with copper, while the W with other surface structures connected well with copper. The results of the shear resistance experiments showed that the micro/nano interface structure significantly improved the shear resistance of W/Cu, where the microgroove structure presented the highest shear strength of 88.19 MPa. It was found that the volume of copper infiltrated into the microstructures had the greatest effect on the thermal shock resistance of the tungsten/copper joint. The highest number of microgroove thermal shock resistance was 297 times. The highest thermal diffusion coefficient of 82.31 mm²/s was obtained for the nanoripple specimens.

Microstructure and phase investigation of FeCrAl-Y2O3 ODS steels with different Ti and V contents

FeCrAl-based steels are considered promising materials for high-temperature nuclear applications. Over the past years, various compositions have been studied to assess their mechanical properties, structural integrity, and radiation damage resistance. However, the microstructure and phase composition of FeCrAl-ODS steels with the addition of different alloying elements are less commonly studied than pure FeCrAl alloys. The paper presents a novel research path for developing FeCrAl matrix ODS steels with Y2O3, Ti, and V additions. The materials synthesis consisted of mechanical alloying of pure metallic components with yttrium oxide in a planetary ball mill under an argon atmosphere. Titanium was added in the amount of 1.0 wt.% to both samples, while 0.5 wt.% of vanadium was added to one sample to verify its impact on the structural stability and hardness. The spark plasma sintering (SPS) technique was used to consolidate the powders. Afterward, the microstructure, chemical composition, phase composition, and hardness were assessed using SEM-EDS, EBSD, TEM-EDS, XRD, XRF, Nanoindentation, and Vickers microhardness. The experimental data reveal rather homogeneous powders after mechanical alloying and dense bulk samples after SPS. The microstructure observations show oxide particles and carbides on the grain boundaries and inside grains of the bcc matrix, which suggests elevated radiation damage resistance. The presence of nanoscale oxide particles (15–50 nm) in the matrix could significantly reduce the impact of aging embrittlement at high temperatures by affecting the chromium diffusion pathways in the ODS steel matrix. The addition of vanadium leads to an improvement of hardness to 4.83±0.43 GPa compared to 3.78±0.34 GPa for the sample without vanadium. Presented experimental results are promising in terms of research and development of FeCr and Al-based ODS materials tailored to operate under harsh conditions in generation IV fission reactors and fusion reactors.

Growth and analysis of polycrystalline silicon ingots using recycled silicon from waste solar module

The proliferated growth of the Photovoltaic industry (PV) will eventually lead to unprecedented volumes of silicon-based solar waste. Failing to manage high volumes of waste, can lead to a huge amount of silicon metal loss and is also highly conducive to posing an environmental hazard. Therefore, efficient recovery and re-utilization after proper purification of the PV-waste-based silicon are highly obligatory for the sustainable development of the PV industry. Herein, we report the growth of small-size silicon ingots (φ = 0.5 inch, 1.0 inch) produced from recovered silicon from the waste crystalline silicon (c-Si) solar module through the Spark Plasma Sintering (SPS) technique. The silicon feedstock was prepared, after the extraction of silicon cells from the used panel and chemically etching contacts, ARC (anti-reflection coating), from the cells in order to recover the silicon wafer. The silicon wafer pieces were pulverized to produce very fine powder and subsequently processed at a different set of temperature-pressure for the study of density variation. The highest density (2.33 gm/cm3) equal to the theoretical density of silicon was obtained for sample grown at temperature 1200 °C and pressure 60 MPa. The purity of the obtained ingots was found to be greater than 3 N and therefore, can find use in different industries.

Enhanced electrical performance in CaBi4Ti4O15 ceramics through synergistic chemical doping and texture engineering

High-temperature piezoelectric materials with excellent piezoelectricity, low dielectric loss and large resistivity are highly desired for many industrial sectors such as aerospace, aircraft and nuclear power. Here a synergistic design strategy combining microstructural texture and chemical doping is employed to optimize CaBi4Ti4O15 (CBT) ceramics with bismuth layer structure. High textured microstructure with an orientation factor of 80%–82% has been successfully achieved by the spark plasma sintering technique. Furthermore, by doping MnO2, both advantages of hard doping and sintering aids are used to obtain the excellent electrical performance of d33 = 27.3 pC/N, tanδ∼0.1%, Q31∼2,307 and electrical resistivity ρ∼6.5 × 1010 Ω·cm. Up to 600 °C, the 0.2% (in mass) Mn doped CBT ceramics still exhibit high performance of d33 = 26.4 pC/N, ρ∼1.5 × 106 Ω·cm and tanδ∼15.8%, keeping at an applicable level, thus the upper-temperature limit for practical application of the CBT ceramics is greatly increased. This work paves a new way for developing and fabricating excellent high-temperature piezoelectric materials.

Calculating the interdiffusion coefficient in TaC/VC diffusion couple and investigation of solid solution formation and mechanical properties

Owing to high-temperature melting and high hardness besides the mutual solubility, TaC-VC binary system is being developed to apply in aggressive and high-temperature environments. This research aims to investigate the solid solution formation of the TaC-VC binary system as well as calculate their diffusion coefficient in each other by the Boltzmann-Matano method. So, three compositions of the TaC-XVC binary system (X = 25, 50, and 75 mol%), as well as a TaC/VC diffusion couple sample, were sintered at 1850 °C for 20 min at 40 MPa pressure via spark plasma sintering (SPS) technique. It was found the maximum relative density and hardness values of 98.1 % and 24.6 GPa were obtained for the TaC-75 mol% VC composite specimen. A slight increment in fracture toughness was observed from 50 to 75 mol% VC and reached 4.7 MPa m0.5 in the TaC-75 mol% VC sample. The XRD results showed V diffuses to TaC crystal lattice and creates (TaXV1−X)C solid solution in TaC containing 25 and 50 mol% VC while in TaC-75 mol% VC, dominantly Ta diffuses in VC and (VXTa1−X)C solid solution is formed. Finally, the interdiffusion coefficients of V into TaC and Ta into VC lattice were calculated as 3.4 * 10−10 cm2 s−1 and 1.3 * 10−10 cm2 s −1, respectively by SEM/EDS analyses in the TaC/VC diffusion couple sample.

Development of TiCN-Co-Cr3C2-Si3N4-based cermets with improved hardness and toughness for cutting tool applications

ABSTRACT A TiCN-Co-Cr3C2-based cermet, with the addition of 5wt. % and 10wt. %Si3N4 and a reference sample without Si3N4 addition were prepared by the spark plasma sintering technique. The average hardness and fracture toughness of the 90TiCN-5Co-5Cr3C2(SN00) cermet-sintered specimens were e14.85±3.11 GPa and 6.78±0.61 MPaÖm, respectively. The cermet composition 85TiCN-5Co-5Cr3C2-5 wt. % Si3N4(SN05) enhanced the hardness and fracture toughness to 20.90±0.825 GPa and 7.23±0.45 MPaÖm, respectively. Further addition of 10 wt%Si3N4 with 80TiCN-5Co-5Cr3C2(SN10) decreased the hardness value to 16.18±0.279 GPa due to a decrease in the density of defects. However, the fracture toughness steadily increased to 9.34±3.10 MPaÖm. The cermet composition 85TiCN-5Co-5Cr3C2-5Si3N4 (SN05) showed an appreciable improvement in hardness and toughness values due to the formation of a core-rim structure, with the core consisting of TiCN and the rim with TiN, TiO2, TiSi, Co2C, CrN and Cr2Si.

Densification, microstructure, and mechanical properties of sintered TiAl-NbN composites

Unlocking the full potential of intermetallic TiAl alloys in aerospace and automotive engines demands critical attention, as their limitations, particularly due to the room temperature brittle nature, inadequate oxidation and strength beyond 800 °C. Hence, the need to improve the mechanical properties is crucial to expanding their versatile applications. Herein, the effect of Niobium nitride (NbN) addition on the densification, microstructure, and mechanical characteristics of Titanium aluminide (TiAl) was studied. TiAl powders with various concentrations of NbN at 0, 2, 4, 6, 8, and 10 wt.% were synthesized through the spark plasma sintering technique. Each blended composite powder was measured according to stoichiometry into a 30 mm internal diameter graphite die and sintered at a temperature of 1150 °C, a pressure of 50 MPa, a heating rate of 100 °C/min, and a dwell time of 10 mins. The densification phenomenon, phase present, microstructure, and mechanical properties were investigated via Archimedes’ principle, X-ray diffraction (XRD), and Vickers hardness tester, respectively. Results shows that the addition of NbN to TiAl at constant sintering parameters enhanced the mechanical properties of TiAl. The microhardness of the composite material increases as the NbN addition increases, with maximum hardness of 467 HV, and ultimate tensile strength (UTS) up to 1458.9 MPa, attained at 10 wt.% NbN addition. Maximum porosity content of an impressive 1.6% was recorded at the addition of 10 wt.% NbN, which shows exceptional efficiency of spark plasma sintering technique. The results on densification and mechanical properties are presented and discussed with respect to the material composition and processing condition of the sintered materials.

Microstructural, Mechanical, and Electrochemical Characterization of CrMoNbTiZr High-Entropy Alloy for Biomedical Application.

High-entropy alloys (HEA) with superior biocompatibility, high pitting resistance, minimal debris accumulation, and reduced release of metallic ions into surrounding tissues are potential replacements for traditional metallic bio-implants. A novel equiatomic HEA based on biocompatible metals, CrMoNbTiZr, was consolidated by spark plasma sintering (SPS). The relative sintered density of the alloy was about 97% of the theoretical density, indicating the suitability of the SPS technique to produce relatively dense material. The microstructure of the sintered HEA consisted of a BCC matrix and Laves phase, corresponding to the prediction of the thermodynamic CALPHAD simulation. The HEA exhibited a global Vickers microhardness of 531.5 ± 99.7 HV, while the individual BCC and Laves phases had hardness values of 364.6 ± 99.4 and 641.8 ± 63.0 HV, respectively. Its ultimate compressive and compressive yield strengths were 1235.7 ± 42.8 MPa and 1110.8 ± 78.6 MPa, respectively. The elasticity modulus of 34.9 ± 2.9 GPa of the HEA alloy was well within the range of cortical bone and significantly lower than the values reported for commonly used biomaterials made from Ti-based and Cr-Co-based alloys. In addition, the alloy exhibited good resistance to bio-corrosion in PBS and Hanks solutions. The CrMoNbTiZr HEA exhibited an average COF of 0.43 ± 0.06, characterized mainly by abrasive and adhesive wear mechanisms. The CrMoNbTiZr alloy's mechanical, bio-corrosion, and wear resistance properties developed in this study showed a good propensity for application as a biomaterial.

Microstructure, electrical conductivity and mechanical properties of CoCrFeNi-Cu composite

For investigating the effect of the admixture method of CoCrFeNi high-entropy alloys (HEAs) in Cu matrix composites on its microstructure and properties, the mechanically mixed CoCrFeNi-Cu powder, and gas atomization CoCrFeNi-Cu powder are prepared by spark plasma sintering technique, respectively. Several intermediates with core-shell structure exist in the specimen which is prepared using CoCrFeNi-Cu powder owing to the inter-elemental diffusion. It is assumed that the core-shell structure is effective in hindering grain deformation during cold rolling process and thus improves mechanical properties of the composites. The electrical conductivity, microhardness, and predicted ultimate tensile strength of the specimen prepared by mechanical mixing of Cu and CoCrFeNi powders were 69.09% IACS, 139.93 HV and 525.9 MPa, respectively.

Excellent tensile yield strength with ultrafine grain and tailored microstructure in plastically deformed Ti–Re alloys

The pursuit of strong and ductile titanium alloys for critical structural applications remains a constant focus in metallurgical engineering research. To evaluate the microstructure evolution and strengthening effect of Rhenium (Re) addition, binary alloys of Ti–xRe (x = 0, 2, 4, 6 wt%) were fabricated via spark plasma sintering and hot extrusion techniques. Microstructure characterization by electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) revealed the presence of equiaxed α and β phases in the extruded materials, with an increased fraction of β phase corresponding to higher Re concentrations. X-ray diffraction (XRD) analysis indicated lattice expansion in the β phase due to Re diffusion, suggesting solid solution formation and preferential diffusion of Re into the β phase. Moreover, Re increments of 4 and 6 wt% resulted in significant grain refinement towards the formation of ultrafine grains (0.8 and 0.6 µm, respectively). The extruded Ti–Re alloys exhibited a linear strengthening trend, with an increase of 250–300 MPa per 2 wt% Re added. The yield strength of Ti–6Re exceeded three times higher than that of commercially pure (CP) Ti produced via a similar process, while maintaining over 13 % elongation. Re increment was also found to influence the deformation behavior of the extruded Ti–Re alloys during tensile test. This comprehensive investigation provides valuable insights into the microstructural changes and strengthening mechanisms associated with the addition of Re in titanium alloys, contributing to the ongoing efforts in developing high-performance materials for critical structural applications.

Characterization of pulse electric current sintered Ti-6Al-4V ternary composites: Role of YSZ-Si3N4 ceramics addition on structural modification and hydrogen desorption

In this study, we fabricated Ti-6Al-4V composites using pulse electric current (spark plasma) sintering technique and examined the influence of yttria-stabilized zirconia (YSZ) and silicon nitride (Si3N4) particles on microstructural, mechanical properties. Moreover, we investigated the effects of YSZ and Si3N4 on hydrogen uptake rate of the fabricated composites. The formation of new phases in addition to the parent α and β phases corroborates the increased hardness property exhibited by the Ti-6Al-4V composites. Further, the improvement in the hardness property was ascribed to Orowan strengthening effect due to resistance offered by cross dislocation pinning effect of closely packed particles. From the nanomechanical test, the penetration depth of the unreinforced Ti-6Al-4V alloy was maximum at a value of 272.57 nm, while all the reinforced alloys exhibited reduced penetration depth, thereby increasing the stiffness and strength of the Ti-6Al-4V composites. Other nanomechanical analyses such as nanohardness, elastic modulus, and creep were also improved in the reinforced composites in comparison with the Ti-6Al-4V alloy. The amount of hydrogen absorbed by the specimens was measured, and the Ti-6Al-4V composite with the highest proportion of Si3N4 reinforcement exhibited the highest hydrogen concentration.

Graded microstructure and mechanical properties of spark plasma sintered Fe-Cr alloys

Developing graded microstructure and mechanical properties is critical for accelerating the design and optimization of structural materials for a wide range of applications. In this study, Fe-Cr alloys were fabricated by spark plasma sintering (SPS) technique. The microstructure, microhardness, and tensile properties of the as-fabricated and thermally annealed variants were investigated. Graded grain structures were created in the as-fabricated cylinders along both axial and radial directions. Grain size was gradually reduced from the sample periphery to the center. Microhardness measurements reveal a gradual decrease of hardness towards the periphery of the samples. The as-fabricated Fe-Cr alloys show a desired combination of tensile strength and elongation, primarily due to the formation of a high density of oxides, voids, dislocations, and grain boundaries. After in-situ thermal annealing at 600 °C under 60 MPa for 2 h using SPS, the Fe-Cr alloys underwent minimal grain growth, and the graded grain structures were retained. The hardness was more uniformly distributed in the annealed variants, and the tensile strength was reduced with an increase in the total elongation, which is attributed to the dissolution of nano-sized oxide particles and the relief of the residual stress. This study demonstrates that SPS coupled with subsequent heat treatment can tailor the graded microstructure and control the mechanical properties of Fe-Cr alloys, showing potential applications in other alloy systems.

Preparing and Wear-Resisting Property of Al2O3/Cu Composite Material Enhanced Using Novel In Situ Generated Al2O3 Nanoparticles.

Al2O3/Cu composite material (ACCM) are highly suitable for various advanced applications owing to its excellent properties. In the present work, a combination of the solution combustion synthesis and hydrogen reduction method was first employed to prepare Al2O3/Cu composite powder (ACCP), and subsequently ACCM was prepared by employing spark plasma sintering (SPS) technique. The effect of Al2O3 contents and SPS temperatures on the properties (relative density, hardness, friction coefficient, and electrical conductivity, et al.) of ACCM were investigated in detail. The results indicated that ACCM was very dense, and microstructure was consisted of fine Al2O3 particles evenly distributed in the Cu matrix. With the increase of SPS temperature, the relative density and hardness of ACCM had first increased and then decreased. At 775 °C, the relative density and hardness had attained the maximum values of 98.19% and 121.4 HV, respectively. With the increase of Al2O3 content, although the relative density of ACCM had gradually decreased, nevertheless, its friction coefficient had increased. Moreover, with the increase of Al2O3 contents, the hardness of ACCM first increased and then decreased, and reached the maximum value (121.4 HV) with 3 wt.% addition. On the contrary, the wear rate of ACCM had first decreased and then increased with the increase of Al2O3 contents, and attained the minimum (2.32 × 10-5 mm3/(N.m)) with 3 wt.% addition.

Characterization of the mechanical and tribological properties of TiO2/polyimide nanocomposites produced using spark plasma sintering method

ABSTRACT In the current study, the enhancement of the mechanical and tribological behavior of polyimide (PI) composites with varying TiO2 nanoparticles fabricated with spark plasma sintering (SPS) technique was examined. The morphology, mechanical, and tribology of the produced nanocomposites were characterized using scanning electron microscope (SEM), nanoindenter, and tribometer analyzer. The SEM result shows that the TiO2 were diffused uniformly in the polymer matrix. The hardness and modulus of the PI increased with the incorporation of the TiO2 nanoparticles by 314.1% and 76.4%, respectively. Furthermore, the friction coefficient and wear resistance of the nanocomposites was remarkably improved with the TiO2 incorporation.