Low-energy Ball Milling Research Articles

The effect of high-energy ball milling on enhancing the mechanical properties, light transmittance, and thermal shock resistance of bone china porcelain

A bone china grouting slurry was prepared using two different milling methods: low-energy ball milling (Named LBC) for 24 h and high-energy ball milling (Named HBC) for 1 h. Bone china green bodies were formed by grouting, and the dried green bodies were calcined at different temperatures points in the temperature range from 1235 °C to 1255 °C. The slurry characteristics, as well as the structure and properties of the calcined samples, were analyzed and evaluated. The particle sizes of LBC and HBC slurry D50 are 5.819 μm and 3.571 μm, respectively, accounting for 80.4% and 98.7% of their respective proportions. The particle size distribution range of HBC samples was relatively concentrated, and the viscosity of the two slurries was 1040 mPa·s and 2800 mPa·s, respectively. The ball milling method significantly influenced the formation of product phases. The content of calcium feldspar and β-TCP phases in HBC samples calcined at 1245 °C was higher than that in their LBC counterparts, while the quartz content in LBC was higher than that in HBC samples. The water absorption and porosity of the HBC samples were lower than those of the LBC samples, with a flexural strength of 205 MPa, heat shock temperature difference of 190 °C, and light transmittance of 5.18%/3.73 mm, which were 22.4%, 26.7%, and 4.2% higher than those of the LBC samples, respectively. These results indicate that bone china prepared using the high-energy ball milling method exhibits excellent performance.

Effect of aging temperature on microstructure and mechanical properties of (Ti1400+TiC)/Ti6Al4V composites

Titanium matrix composites, due to their high strength, high modulus, and high temperature resistance, have become ideal materials that meet the lightweight and high-performance requirements in the aerospace industry. However, their poor ductility remains a key issue that restricts their widespread application. In this study, (Ti1400+TiC)/TC4 composites were prepared by low-energy ball milling and spark plasma sintering and subjected to solution treatment and aging treatment. The effects of aging temperature on the composition, microstructure, and mechanical properties of the composites were analyzed, and the strengthening mechanism of (Ti1400+TiC)/TC4 composites was discussed. The aging temperature between 350 ℃ and 700 ℃ had little effect on the microstructure of TC4 matrix and the discontinuous three-dimensional network structure of TiC particles. As the aging temperature increased, the elongated α-phase within the Ti1400 region became shorter and thicker, and Cr’s rapid diffusion resulted in β-phase being more widely distributed. After aging at 600 ℃, the tensile strength of the composite was 1202 MPa, and its total elongation reached 11.3 %, showing excellent strength-plasticity matching. The mechanical properties of composites are mainly affected by the microstructure in the Ti1400 region. The elongated α-phase in the Ti1400 region provides high strength for the composite. The thicker α-phase and the widely distributed β-phase led to more uniform strain within the composite, avoiding premature fracture caused by stress concentration near TiC particles and promoting ductility in the composite.

Investigation of microstructure and thermal expansion behaviour of a functionally graded YSZ/IN718 composite produced by laser-powder bed fusion

Yttria-stabilized zirconia (YSZ) has been extensively used as a thermal barrier coating (TBC) for high-temperature alloys. In this research, the microstructural attributes and thermal expansion behavior of an additively manufactured functionally graded composite (YSZ/IN718 FGC) were investigated. First, a powder mixture of IN718 and YSZ (ranging from 1 wt% to 4 wt%) was achieved via low-energy ball-milling at 100 rpm. Differential scanning calorimetry (DSC) analysis depicted the melting behaviour of the powder mixtures of different YSZ content. The endothermic peaks in the DSC curve, at ∼1360 ℃, suggested that the energy needed to melt the powder mixture increases with increasing YSZ content. These varying powder compositions were used to fabricate FGC samples using L-PBF. The study investigated the effects of laser power variation along the YSZ gradient, successfully mitigating the fusion defects that had been initially observed in FGC samples. Microscopic analyses, comprising scanning electron microscopy (SEM) and transmission electron microscopy (TEM), depicted the elemental segregation of Nb and Mo at the solidification subgrain boundaries (SSBs). Furthermore, the electron backscattered diffraction (EBSD) results demonstrated the refinement of grains and a reduction in textural intensity, particularly along the YSZ gradient. Energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA) were used to validate the uniform dispersion of YSZ particles throughout the composite matrix, with the EPMA line scan affirming a predominantly linear YSZ content variation. Lastly, the coefficients of thermal expansion (CTEs) were evaluated, both parallel and perpendicular to the build direction. A decrease of approximately ∼6 % in CTE was noted along the building or gradation direction. Notably, perpendicular to the building direction, the CTE values for specimens containing 4 wt% and 2 wt% YSZ witnessed significant reductions of ∼32 % and ∼12 %, respectively. This research significantly contributes to the understanding of the microstructural intricacies and thermal behavior of YSZ/IN718 FGC produced by L-PBF process.

Mechanical properties of additively manufactured ultrafine grain stainless steel-titanium boride (SS–TiB2) nanocomposites

Stainless-steel, particularly the 316L alloy, is extensively utilized across diverse industrial sectors. Nonetheless, its inherent limitation of low yield strength poses a significant challenge. In this study, we propose a novel method to address this limitation by incorporating trace quantities of TiB2 nanoparticles into the 316L matrix. The methodology involves a combination of low-energy ball milling for the preparation of the powder feedstock, followed by selective laser melting (SLM) for the fabrication of nanocomposites. The resulting stainless-steel nanocomposite exhibits a nearly-full dense structure characterized by the uniform dispersion of TiB2 nanoparticles (30–40 nm in diameter) within the matrix grain interiors and at grain boundaries. This leads to a substantial refinement in the matrix grain and a remarkable enhancement in mechanical properties. Specifically, the incorporation of 3 vol% TiB2 nanoparticles results in substantial enhancements in tensile yield strength (90.5 %), microhardness (81.4 %), ultimate strength (78.03 %) and bulk modulus (75.2 %) at room temperature compared to plain SLMed stainless-steel. This notable enhancement arises from the uniform dispersion of TiB2 nanoparticles and grain refinement, achieved without discernible processing defects such as agglomeration or interface microcracks. These findings offer a promising avenue for enhancing the mechanical characteristics of stainless-steel-based nanocomposites, thereby expanding their applicability in demanding engineering environments.

Microstructure Analysis and Powder Bed Fusion of Inconel 738 Powder Materials Mixed with Nano-Sized Ceramic Powders

Powder materials strengthened by oxide dispersion are generally made by in-situ method; direct oxide dispersing in matrix powders during atomization. There is also ex-situ method; oxides dispersing by mixing with matrix powders. In this study powder mixtures (Inconel 738 matrix powder + SiO2 powder + Al2O3 powder) were mechanically manufactured by ex-situ process, a lowenergy ball milling method. Then, specimens of the as-mill powders were manufactured by laser powder bed fusion (L-PBF) method and spark plasma sintering (SPS) process. The microstructures of each prepared specimen were compared according to process variables. SEM, EDS, XRD, and Electron Backscatter Diffraction (EBSD) analyses were applied in this study.

Feasibility study on mass-production of oxide dispersion strengthened Cu alloys for the divertor of DEMO fusion reactor

Oxide dispersion strengthened Cu (ODS Cu) alloys possess a high potential to be used as promising heat sink materials for the divertor system in DEMO fusion reactors. Considering their future application in fusion reactor divertor systems, mass-production of ODS Cu alloys is a must. The purpose of this study is to investigate the feasibility of large-scale production of ODS Cu alloys by improving the production process based on the already established mass-production process of ODS Fe alloys in cooperation with the steel manufacturer Kobelco Research Institute. After optimization of the mechanical alloying (MA) parameters, a large-scale production of ODS Cu powders was successfully achieved with a recovery rate of over 90% and around 1Kg powder in one batch production using an industry-level attritor ball mill cooled by circulating water. The mass-produced ODS Cu alloys were comprehensively characterized, including mechanical properties, microstructure and thermal diffusivity, and a new concept of low-energy ball milling was proposed based on the results to realize the mass-production of ODS Cu alloys.

Insight into the slope-plateau capacity behaviour of polymer-derived silicon oxycarbide anodes in Na-ion batteries

Silicon oxycarbide-based amorphous ceramic material was prepared by crosslinking and step-wise pyrolysis of polysiloxane-based Polyramic resin at temperatures up to 1200 °C as a matrix for anode in Na-ion batteries (NIBs). The synthesized powder was milled under low and high energy ball milling (LEM, HEM) conditions to investigate the effect of powder characteristics on the electrochemical properties of anodes in NIBs. The XPS and EDX analyses showed that the chemical compositions of anodes prepared from LEM and HEM SiOC were similar. However, the SiOC anodes prepared from finer grain sized HEM SiOC powders exhibited better performance like lower charge transfer resistance and faster Na+ diffusion coefficient. The slope capacity and thereby the total specific capacity was enhanced in HEM-SiOC anode. Therefore, the refinement of the particle size and increased surface area are vital for producing high-energy density SiOC anodes for NIBs.

Enhanced properties of titanium matrix composites via in-situ synthesized TiCx and Ti5Si3 with network structure

In-situ network-structured (TiCx + Ti5Si3)/TC4 composites were fabricated via a low-energy ball mill and hot-pressing sintering based on the reaction between Ti3SiC2 and Ti. The microstructure evolution, mechanical properties, and tribological behavior of the composites with different amounts of Ti3SiC2 were studied. The experimental results show that the microstructure of the matrix transforms into the equiaxed structure with the addition of Ti3SiC2. The in-situ TiCx particles are mainly distributed around the matrix and form a network structure, as the Ti3SiC2 content is 5 vol%. Compared with neat TC4, the hardness, tensile strength, and wear resistance of the composites can be significantly enhanced. Moreover, the composite with 5 vol% Ti3SiC2 displays excellent comprehensive properties. The tensile strength of the composite is 1165 MPa, increased by 34.7 % over the neat TC4 and its elongation reaches 8.5 %. Meanwhile, the wear rate of the composite decreases to 24.5 × 10−5 mm3/(N·m), which is reduced by 16.7 % compared with the neat TC4. It is worth noting that the aggregation of particles can seriously reduce the mechanical properties of the composites.

Constructing micro-network of Ti2Cu and in-situ formed TiC phases in titanium composites as new strategy for significantly enhancing strength

Titanium matrix composites (TMCs) with homogeneous microstructures often exhibit inferior mechanical properties including low strength and poor ductility, thus severely restricting their wide-range applications as engineering structural parts. Herein, we designed a hybrid structured (TiC + Ti2Cu)/TC4 composites consisting of TiC particles and micro-network structures of Ti2Cu, using reduced graphene oxides (rGO) and copper nano-powders as precursors via a two-step low energy ball milling and spark plasma sintering. These in-situ formed TiC particles were uniformly distributed within the TC4 matrix, whereas Ti2Cu nanoparticles were generated by the eutectoid reaction and distributed at the α/β phase interfaces, forming a micro-network structure within the titanium alloy matrix. Sizes, morphologies, distributions and fractions of Ti2Cu structures were adjusted by controlling the Cu contents, and these play dominant roles in determining tensile properties of the composites. The fabricated (TiC + Ti2Cu)/TC4 composites exhibit significantly higher tensile strengths than that of the monolithic TC4 (increased by 32.2 %), which is mainly attributed to the refinement strengthening from TiC + Ti2Cu hybrid reinforcements and precipitation strengthening from Ti2Cu with micro-network structures. This study develops a new methodology to significantly improve the tensile strength of carbonaceous nanomaterial reinforced titanium matrix composites.

Parametric investigation and optimization in laser based directed energy deposition of tungsten carbide-cobalt

Cemented carbide (WC-Co), the widely used tool-die material, is difficult to be machined by conventional and nonconventional techniques. This inspired exploring additive manufacturing (AM) of this material. However, porosity, brittleness due to cobalt depletion, etc. have been reported in the literature with rare success. For the AM of WC-Co, the current work focuses on directed energy deposition, which can be implemented with existing laser cutting-welding workstations, with modifications. To ensure the retention of cobalt even after inevitable vaporization of some of its initial content during deposition, 20 wt. % of Co was mixed with WC powder by low-energy ball milling. Laser power, scan speed, and powder flow rate were varied following a full-factorial design of experiments. The analysis of variance revealed that the experimental model and most of the parameters were significant. Only the laser power came out to be insignificant for the contact angle. The track height and width increased with the laser power and reduced with the scan speed. The contact angle increased with the scan speed and reduced with the powder flow rate. Cross sections of the deposited track showed no pores or cracks. Multiobjective optimization with gray relational analysis was conducted to get the parameter combination giving high values of the contact angle, track height, and width simultaneously. The optimum parameter combination, thus, obtained is 700 W laser power, 5 mm/s scan speed, and 5 g/min powder flow rate. This yielded 305 ± 40 μm track height, 2132 ± 33 μm width, and 152° ± 2° contact angle.

Formation evolution and strengthening of quasi-continuous network like TiB whiskers in the in-situ TiBw/TC21 matrix composites

In-situ TiBw reinforced TC21 matrix composites with quasi continuous network structure were prepared by low energy ball milling and hot press sintering (HPS) in this work. The microstructure, mechanical properties and strengthening mechanism of TC21 matrix composites reinforced with different volume fraction of TiB were systematically studied. In-situ TiB whiskers with quasi-network structure can significantly refine the β Phase harmony α Phase size. It is also conducive to the formation of equiaxed α-Ti. The research shows that the strength of in-situ TiBw reinforced TC21 matrix composite is significantly better than that of the monolithic TC21 alloy. For example, the YS value and UTS value of in-situ TiBw/TC21 matrix composite containing 5.1 vol% are 1170 MPa and 1268 MPa respectively, which are 34.2% and 23.3% higher than those of the monolithic TC21 alloy under the same process conditions. This paper also analyzes the reason why the theoretical YS value of the composite material is greatly different from the experimental YS value, and believes that it may be that the TiB whisker forms a network structure, which affects the smooth transfer of load from the TiB whisker to the matrix.

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.

Simultaneous Improvement in Strength and Ductility of TC4 Matrix Composites Reinforced with Ti1400 Alloy and In Situ-Synthesized TiC

To overcome the tradeoff between strength and ductility of materials and obtain titanium matrix composites with excellent mechanical properties, in this study, the in situ-synthesized TiC particles and Ti-Al-V-Mo-Cr (Ti1400) alloy-reinforced Ti6Al4V (TC4) matrix composites ((Ti1400 + TiC)/TC4) were fabricated by low-energy ball milling and spark plasma sintering. The inhomogeneous distribution of TiC particles and Ti1400 alloy, as well as the compositional and structural transition zone, were characterized. The TiC/TC4 composite displayed a significantly higher yield strength and tensile strength compared to the TC4 alloy. However, the total elongation of the TiC/TC4 composite was only 57% of that in the TC4 alloy. In contrast, the (Ti1400 + TiC)/TC4 composites exhibited noticeably higher total elongation than the TiC/TC4 composite. Furthermore, the tensile strength of the composite increased with the increase in Ti1400 alloy content. The increase in strength can be attributed to solid solution strengthening and fine grain strengthening. The compositional and structural transition zone, formed by element diffusion, provided a better interface combination between the reinforcements and TC4 matrix. In the transition zone and Ti1400 region, a large number of α/β interfaces can effectively alleviate the stress concentration, and the increase in the β phase can bear more plastic deformation, which is conducive to improving the elongation of the composite. As a result, the (Ti1400 + TiC)/TC4 composites exhibited simultaneous improvements in strength and ductility.

Nd-Fe-B particles with reduced oxygen content and enhanced magnetic properties prepared through reduction-diffusion and novel washing process

The Nd-Fe-B particles with high (BH)max were obtained through a wet chemical method involving reduction–diffusion (RD) and heptane ball milling. The phase purity, microstructure, and magnetic properties of the magnetic particles produced by RD can be affected by the washing process used. In this study, various washing processes, including wet ball milling (WBM) washing with ethanol or heptane and conventional washing with deionized water (DIW) were explored. The WBM washing method involves the low energy ball milling of RD powder in ethanol or heptane instead of several repetitions of water washing steps. This results in the production of Nd-Fe-B particles that exhibit enhanced morphology, phase purity, and magnetic properties when compared to those obtained through the standard DIW process. This is likely due to crushing agglomerates formed during the RD into uniform sized particles and efficient removal of by-products such as Calcium oxide and residual Calcium. In addition, WBM washing in heptane showed high magnetic properties, including a coercivity of 3.9 kOe, remanence of 135 emu/g, and magnetic energy density of 16.7 MGOe. This is thought to be due to the minimal oxidation of Nd-Fe-B particles and absence of an amorphous layer on the surface of the particles. The findings of this study could be useful to produce other high-performance magnetic particles using RD process.

Tailoring a low-energy ball milled MnCo2O4 spinel catalyst to boost oxygen evolution reaction performance

The development of cost-efficient oxygen evolution reaction (OER) catalysts is one of the most important tasks facing modern techniques for hydrogen production. In this work, for the first time, a low-energy ball milling process of MnCo2O4 (MCO) spinel powders, with a mechanical modification time exceeding 1 day was used. After 6 days of ball-milling, the obtained overpotential of the electrocatalyst reached the value of 375 mV at 10 mA cm−2, which is a relatively low value obtained for this type of compound. The studies showed how the mechanical (low-energy long-term milling process) and chemical modification of the fragmented spinel powder nanoparticle surfaces affects the increase of the electrocatalytic properties. The addition of the appropriate amount of conductive carbon black (cCB) and Nafion ionomer to the ink of the MCO spinel also has a significant effect on the improvement of the catalytic performance of the manganese-cobalt oxide during the milling process. By reducing the amount of Nafion to 10 % of its initial value, the overpotential dropped to 352 mV at 10 mA cm−2 after 30 days of ball-milling. This shows that catalyst ink and layer composition are important factors influencing the catalyst’s efficiency in the OER.

New powder metallurgy preparation method of homogeneous and isomeric Al−Cu−Mg mixed crystal materials

A new idea of homogeneity isomerism is proposed in this work to break through the single restriction that traditional homogeneous powder metallurgy materials take refining particles as the only modification method. AA2024 alloy powders of different diameters are mixed in a certain proportion through low-energy ball milling, and then a kind of mixed crystal material is successfully fabricated by hot pressing sintering. The results show that the grain morphology of the traditional sample sintered with single-diameter particles tends to become irregular polygon shape, while the grain morphology of the mixed crystal materials forms a special structure in which larger grains are coated with smaller grains. Compared with the former, when the proportion of coarse particles is 20% (mass fraction), the tensile strength increases by 38.8%; when the proportion of coarse particles is 50%, the elongation increases by 14%. The mixed crystal material exhibits a mixed fracture mechanism of intergranular fracture and transgranular fracture, and the pinning effect of the second phase on the dislocation is more obvious, so the properties of the alloy are improved significantly. The above research provides a new idea for the preparation of high-performance homogeneous isomeric mixed crystal materials.

Investigation of the Effect of Molybdenum Silicide Addition on the Oxidation Behavior of Hafnium Carbonitride

In this study, the oxidation stability up to 1000 °C in air of the Hf(C,N)-MoSi2 composites was explored under non-isothermal and isothermal conditions. Composites with 1, 5, 10, and 20% volume fractions were produced by low-energy ball milling and subsequent spark plasma sintering. Differential scanning calorimetry (DSC) and thermogravimetric (TG) coupled with mass spectrometry were used to reveal the staging of the oxidation process depending on the additive content. It was found that samples containing 1 and 5 vol% MoSi2 had the lowest weight gain and the best oxidation behavior. The results of this study were supported by microstructural and phase analyses of the samples after isothermal treatment in a furnace. The samples with the lowest molybdenum disilicide content had a dense and thin protective oxide film on the surface, consisting of hafnium orthosilicate and monoclinic HfO2. The increase in the amount of MoSi2 contributed to the formation of a loose and porous oxide layer due to the increase in the concentration of volatile MoO3. However, all samples exhibited higher oxidation resistance compared to the pure Hf(C,N).

Effect of low energy milling processes on the magnetic properties of Fe–Ni–Co soft magnetic materials

ABSTRACT This work reports the effect of micro strain of soft magnetic materials obtained by low-energy ball milling. It has been observed that the low energy of the ball milling changes the magnetic domain size, increasing magnetisation, remanence and magnetic permeability of the milled powders as ferromagnetic particles. It is due to the increase of linear defects and the increase of lattice strain. The magnetisation M S increases up to 70% by the accumulation of crystalline defects, although M S decreases with the reduction of particle size, due to the connections of voids between the lines of magnetisation across the crystalline defects obtained by milling. This response is produced by the cold working through the ball milling.

Al-Cu-Mg Alloy Powder Reinforced with Graphene Nanoplatelets: Morphology, Flowability and Discrete Element Simulation

Research in metal matrix composites (MMCs) indicates that superior mechanical properties may be achieved by embedding reinforcement materials. However, the development of new composite powder for additive manufacturing requires an in-depth understanding of its key characteristics prior to its use in the fabrication process. This paper focuses on the low-energy ball milling (LEBM) of aluminium 2024 alloy (AA2024) reinforced with graphene nanoplatelets (GNPs). The main aim is to investigate the effect of the milling time (from 0.5 to 16 h) on the morphology and flowability of the powder. The study shows that, while short milling times (under 2 h) could not break the Van der WaRals forces between nanoparticles, GNPs were well separated and sufficiently covered the powder surface after 4 h of milling, thanks to the continuously applied impact energy. Longer milling time provides increasingly similar flowability results, confirmed by both the experimental work and discrete element model (DEM) simulations. Moreover, the ball milling process decreases the crystallite size of the milled powder by 24%, leading to a 3% higher microhardness. Lastly, the surface energy of the powder was determined as 1.4 mJ/m2 by DEM, using the angle of repose of the as-received powder from experimental work.

Composite powders with carbon nanotubes for laser printing of electronics

The purpose of this work is to develop electrically conductive composite fine powder containing carbon nanotubes, for use in the laser printing technique. This requires the evaluation of several approaches to the mixing of thermofusible powder with carbon nanotubes. For the experiments, a commercial toner for HP laser printer was used as a matrix and multiwalled carbon nanotubes as a conductive phase. Due to the fine powder morphology, carbon nanotubes should also be compatible with the laser printing technique. Several approaches were evaluated for obtaining a fine composite powder with carbon nanotubes, including ultrasonic stirring and low energy ball milling process. The obtained fine powder was tested towards compatibility with a desktop laser printer. Due to the complexity of the laser printing process, we decided to use the thermal transfer method, one of the elements of the laser printing technique. Adhesive properties evaluations and electrical measurements of powders with various amounts of nanotubes (10–30 wt%) were examined. This allowed selecting the composition of 18–20 wt% of carbon nanotubes as optimal, exhibiting proper adhesion to the paper substrate and with resistance in the range of 102 Ω. For the samples with appropriate adhesion to the substrate, we observe a trend of increasing conductivity with increased nanotube content. The developed composite is compatible with the laser printing technique, but it requires higher pressure than applied by commercial laser printers during the process of melting into the paper substrate.