Effect Of Mechanical Milling Research Articles

Effect of High‐Energy Ball Milling on Mechanical Properties of the Mg–Nb Composites Fabricated through Powder Metallurgy Process

New biocompatible and biodegradable Mg–Nb composites used as bone implant materials are fabricated through powder metallurgy process. Mg–Nb mixture powders are prepared through mechanical milling and manual mixing. Then, the Mg–Nb composites are fabricated through cold press and sintering processes. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of Mg–Nb composites are investigated. The mechanical milling process is found to be effective in reducing the size of Mg and Nb particles, distributing the Nb particles uniformly in the Mg matrix and obtaining Mg–Nb composite particles. The Mg–Nb composite particles can be bound together firmly during the sintering process, result in Mg–Nb composite structures with no intermetallic formation, lower porosity, and higher mechanical properties compared to composites prepared through manual mixing. Interestingly, the mechanical properties of manually mixed Mg–Nb composites appear to be even lower than that of pure Mg.

The Effect of Mechanical Milling on Graphite–Boron Carbide Hybrid Reinforced ZA27 Nanocomposites

The main focus of this study is concentrated on the effect of mechanical milling on graphite–boron carbide hybrid reinforced ZA27 nanocomposites. With this respect, nano-sized graphite (Gr) and boron carbide ( $$\hbox {B}_{4}$$ C) reinforced ZA27 matrix nanocomposites were fabricated via a combination of mechanical milling (MM) and hot pressing techniques. MM method was used to produce a ZA27-based hybrid nanocomposite (ZHNC) that nano-sized additives dispersed homogenously in ZA27 matrix. Microstructural and mechanical properties of the nanocomposites were scrutinized as a function of milling time using X-ray diffractometer, scanning electron microscope, hardness and tensile testing machines. Results show that MM method can be utilized for homogeneously distributing the nano-sized additives. Flake-shape morphology negatively influences physical and mechanical properties. It was also found that grain and particle size is decreased after 12 h milling process. With increasing MM time, homogeneous microstructure of the nanocomposite bulk materials was obtained and subsequently their mechanical properties were improved considerably.

Effects of Mechanical Milling and Sintering Temperature on the Densification, Microstructure and Tensile Properties of the Fe–Mn–Si Powder Compacts

This work reported on the effects of mechanical milling and sintering temperature on the densification, microstructure and mechanical properties of the Fe–28Mn–3Si (wt%) alloy. Elemental Fe, Mn and Si powders were used as the starting materials, and two batches of powder mixture were prepared: one was blended elemental (BE) powder mixture; the other was mechanically milled (MM) powder mixture milled for 5 h using planetary ball milling. Both powder mixtures were pressed under a uniaxial pressure of 400 MPa, and subsequently sintered in a high vacuum furnace for 3 h at 1000, 1100, 1200 and 1300 °C. It was found that Mn depletion region (MDR) was formed on the surface of all the sintered samples. The sintered BE compacts had a low density ( γ -austenite and minor e -martensite. In comparison, additional (Fe, Mn) 3 Si phase was observed in the BE alloys sintered at 1000 °C, and a single α -Fe phase was identified in the BE compact sintered at 1300 °C. The tensile properties of the sintered MM compacts increased significantly with the temperature and were significantly higher than those of their BE counterparts.

The effects of mechanical milling on the structural, mechanical, and electromagnetic properties of Cu-8 wt% NdFeB composite alloys

In an attempt to develop new materials that combine structural (mechanical) and functional (electrical and magnetic) properties, a copper composite alloy reinforced through the dispersion of fine Nd2Fe14B intermetallic particles has been synthesized by the powder metallurgy route. Composite master alloy was prepared by blending copper and 8 wt% of intermetallic NdFeB in a planetary ball mill working at 250 r/min under argon atmosphere for 10 h. Resulting composite powders were encapsulated in Cu cans and then consolidated by extrusion at 1023 K. Microstructure features of blended powders and consolidated materials were characterized by means of X-ray diffraction, scanning electron microscopy, and electron probe micro analysis. Fitting of the X-ray diffraction patterns with the Rietveld method revealed that during processing, some NdFeB particles reacted with copper and oxygen to form Nd2CuO4. The lower Nb content on the Nd2Fe14B intermetallic phase due to this oxidation causes the dispersion of Fe and Fe2B particles, which also have soft magnetic properties but a higher moment compared to Nd2Fe14B. The extruded alloys showed enhanced mechanical properties (with yield strength ≥ 600 MPa, ultimate tensile strength ≥700 MPa, and 5% elongation to failure) with satisfactory electrical conductivity (46% IACS) and high values of the coercive field (≥30,000 A/m).

Effects of mechanical milling on the carbothermal reduction of oxide of WC/Co hardmetal scrap

The effects of mechanical milling on the carbothermal reduction of oxidized WC/Co hardmetal scrap with solid carbon were examined. Mixed powders were manufactured by milling the WC/Co hard metal scrap oxide and carbon powder in either a tumbler-ball mill or a planetary-ball mill. The milling type affected the carbothermal reduction of the oxide owing to the differing collision energies (mechanical milling energies) in the mills. The hardmetal scrap oxide powder (WO3, CoWO4) milled at high energy was more greatly reduced and at a lower temperature than that milled at lower mechanical energy. The formation of WC by the carburization reaction with solid carbon reached completion at a lower temperature after higher-energy milling than after lower-energy milling. The WC/Co composite particles synthesized by the combined oxidationmechanical milling-carbothermal reduction process were smaller when the initial powder was milled at higher mechanical energy.

Influence of high energy milling on the microstructure and magnetic properties of the Al–Cu–Fe phases: the case of the i-Al64Cu23Fe13quasicrystalline and the ω-Al70Cu20Fe10crystalline phases

The effect of mechanical milling in i-Al64Cu23Fe13quasicrystalline and ω-Al70Cu20Fe10crystalline phases is systematically investigated in the present work.

Influence of mechanical milling on structure, particle size, morphology and magnetic properties of rare earth free permanent magnetic Zr2Co11 alloy

In an effort to explore finding rare earth free permanent magnet material for device applications, the Co based Zr2Co11 compound has been selected for investigation. A detailed study was carried out on the effect of mechanical milling on structure, particle size, morphology and magnetic properties. The alloy of nominal composition Zr18Co82 exhibited co-existence of minor Zr6Co23 phase along with main phase Zr2Co11. When subjected to long duration mechanical milling, the alloy has undergone structural disorder leading to partial amorphization. The particle size has decreased from 200 μm to 120 μm up on milling for 6 h in a planetary milling process. Further milling caused less influence on particle size reduction. However, it had an effect on particle size distribution. The size reduction is not very high due to ductile nature of Zr2Co11 phase and the morphology of the particles too showed coarse plate shape. The coercivity variation against particle size reduction is less than appreciable, given that the crystal structure being rhombohedral with significant magnetocrystalline anisotropy. The defects induced during milling and the presence of deleterious minor phases are considered the main cause for reduction in the coercivity.

Influence of mechanical milling conditions on the dispersity of lithium ferrite

The effect of mechanical milling in a planetary ball mills on dispersity of the synthesized lithium ferrite powder was investigated by laser diffraction technique. The mechanical milling of powder was carried out by two planetary ball mills: SPEX 8000M and Fritsch Pulverisette 5 with different time period. The lithium ferrite powder was milled for 30, 60 and 120 minutes in the first ball mill. The powder milled for 60 minutes in the second ball mill was performed. The results showed that an increase in the milling time slightly decreases the average particle size of the ferrite powder in case both ball mills. However, only milling in a SPEX planetary mill increases homogeneity of the ferrite powder, while the milling in Fritsch causes intensive processes of particle aggregation.

Effect of mechanical milling on the microstructure of tungsten under He+ irradiation condition

“Pure” W was prepared through a powder metallurgy route by using hard alloy (WC–Co) milling tank and balls to mill WO3 powder, reducing with high purity H2, and sintering with spark plasma sintering technique. XRD, SEM, and TEM were used to characterize the phase and phase structures. Results showed that the cobalt tungsten carbide (Co3W10C3.4) phase was induced from the milling tank and balls. After the “pure” W bulk was exposed to helium ions for 2h, the cobalt tungsten carbide phase was found to be surrounded by the lattice distortion phase of W, which showed high irradiation resistance.

Effect of mechanical milling on the structural and dielectric properties of BaTiO 3 powders

Barium titanate (BaTiO3) is a well-known ferroelectric material and widely used in electronic industries for the multi-layer ceramic capacitor. In this reported work, commercially available tetragonal BaTiO3 (BT) powders were taken to study the size effect on the structural and dielectric properties of the BT ceramics during high-energy ball milling (0–110 h). The same perovskite when kept under a normal atmospheric condition after milling shows gradual increase of additional crystalline phase that occurred because of the absorption of atmospheric CO2 gas, which is characterised as orthorhombic BaCO3. The milled BT samples were characterised by X-ray diffraction and small-angle X-ray scattering and a dielectric analyser. The purpose of this work was to study how the dielectric property of nanoBT ceramics varies with reduction of particle size, structural changes and the absorption of carbon by these nanopowders. It was observed that the dielectric constant of the BT powders increases with particle size reduction during milling. The dielectric behaviour of the BT ceramics significantly changes with polymorphic phase transformation in nanocrystalline BT at different stages of milling. The capacitance of nanoBT powders is significantly changed with the absorption of carbon by the nanoBT powders in a humid atmosphere.

The effect of mechanical milling on the soft magnetic properties of amorphous FINEMET alloy

The effect of milling time on the magnetic properties of FINEMET amorphous ribbons has been investigated using X-ray diffraction, Mössbauer spectroscopy, thermo-magnetic measurements, transmission electron microscopy and SQUID magnetometery. Ribbons were melt-spun at a wheel speed of 38 ms-1 and then mechanically milled for different periods up to 45 min. The results showed that the partially crystallization of the amorphous powder occurs during milling. TEM observations confirmed the formation of small volume fraction of the crystalline phase with ~9 nm crystallite size in the amorphous matrix for the ribbon milled for 45 min. Thermo-magnetic measurements indicated the enhancement of the Curie temperature of amorphous phase during milling which is due to the annihilation of free volumes and microstructural ordering. The Hopkinson effect led to the monotonic increase of magnetization with respect to the temperature before reaching the Curie temperature of the milled samples. Moreover; the magnetization increased with the formation of the Fe(Si) phase while the coercivity decreased. Mössbauer spectroscopy and thermo-magnetic measurements revealed the existence of 13% Fe in crystalline phase. The composition of crystalline phase was determined as Fe–16.5Si. Hyperfine field values increased with milling time, suggesting the ordering of the structure and enhancement of the number of Fe–Fe atomic pairs in the crystalline phase comparing to the primary amorphous ribbon.

Effect of mechanical milling on nanocrystalline grain stability and properties of Cu–Al2O3 composite prepared by thermo-chemical technique and hot extrusion

In this study, an influence of mechanical milling on the structural characteristics, mechanical properties and electrical conductivity of the ultrafine Cu–3vol.% Al2O3 composite is analyzed. The initial Cu–Al2O3 powder was prepared by in situ thermo-chemical technique. Compared are two samples prepared by compacting of the non-milled and the intensively milled powder. The milling process ensured additional powder refinement and uniform distribution of secondary nano-particles in the Cu matrix. In the process of hot extrusion and annealing of the compact at elevated temperatures, the particles effectively strengthened crystallite/grain boundaries. Therefore, the composite has a homogeneous, thermal stable nanostructure up to 900°C, good hardness of 130HB and yield strength of 235MPa. The composite prepared from the non-milled powder is characterized by a bimodal grain size microstructure, low hardness of 80HB, lower yield strength of 185MPa and it is structurally stable only up to 200°C as a consequence of recrystallization processes and grain growth. The electrical conductivity of both materials is sufficient for electrotechnical applications.

Effect of Mechanical Milling on the Morphologyand Structural Evaluation of Al-Al2O3 Nanocomposite Powders

The morphological and microstructural changes during mechanical milling of Al powder mixed with 2.5, 5 and 10 wt.% Al2O3 particles were studied. The milling was performed in a planetary ball mill for various times up to 20 h. The produced composite powders were investigated using X-ray diffraction pattern (XRD) to elucidate the role of particle size, secondary phase content and milling time on grain size and lattice strain of Al matrix. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson–Hall formula. To investigate the morphological changes by the scanning electron microscopy (SEM) analysis. The results show that the addition of hard Al2O3 particles accelerates the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Furthermore, Al becomes smaller crystallite size during ball milling of Al powder in the presence of Al2O3 particles. The results revealed that the grain size of milled powders was about 45 nm with a noticeable presence of agglomerates. Uniform distribution of nano-sized Al2O3 particles in the Al matrix could be achieved with increasing milling time.

Effect of mechanical milling on electrochemical properties of Ti45Zr38xNi17+x (x=0, 8) quasicrystals produced by rapid-quenching

The effect of mechanical milling on the discharge performance of electrodes consisting of Ti45Zr38−xNi17+x (x = 0, 8) quasicrystals, which were produced by a rapid-quenching, was investigated at room temperature in three-electrode cell set-up. All of the obtained ribbons were identified to contain mostly icosahedral (i) quasicrystal phase (i-phase). The measured discharge capacity for Ti45Zr30Ni25 material was higher than the one for Ti45Zr38Ni17. The maximum discharge capacity equal 86 mA h g−1 was achieved for Ti45Zr30Ni25, which was mechanically milled for 15 h. This value was obtained at the third discharge process. The recorded discharge performance was quite stable on cycling up to 30 cycles for Ti45Zr38Ni17 material, but slight decrease after 15th cycle was observed for Ti45Zr30Ni25 phase. It should be highlighted that the quasicrystal i-phase remained stable also after 25 h of mechanical milling for both studied materials. However, a formation of (Ti, Zr)H2 hydride phase was observed after charge/discharge cycles for both of the materials.

Effect of Mechanical Milling on Structure, Morphology and Electrochemical Performance of Zinc Oxide Powders

ZnO powders were treated by mechanical milling. The structure and morphology of ZnO powders milled for different periods were characterized by XRD and SEM. The discharge behavior and cycle life of ZnO electrodes in Zn/Ni batteries were studied by galvanostatic charge and discharge tests. The incorporation of cycle voltammetry was adopted to investigate charge and discharge mechanisms of ZnO electrodes. The results showed that the grain size of the powders decreased from 135.6 nm to 17.9 nm while the lattice strain increased from 0.06% to 0.57% during milling, which could be attributed to the formation and movement of dislocations. The electrochemical reaction activity of ZnO powders was improved by mechanical milling, resulting in an increase of discharge capacity. ZnO powders milled for 100 h shows a high discharge capacity of 300.6 mAh/g, which is 50 mAh/g higher than that of the unmilled ZnO powders.

Preparation and Crystallization of Nd<sub>2</sub>Fe<sub>14</sub>B/<i>α</i>-Fe Permanent Magnetic Nanomaterial by Mechanical Milling

Nanocomposite Nd2Fe14B/α-Fe magnetic material had been prepared by mechanical milling Nd8Fe86B6 as-cast alloy in Argon and subsequent crystallization. Effect of mechanical milling and crystallization technique on its structure had been investigated by means of X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Caborimetry (DSC), etc. The crystallization behavior of amorphous Nd8Fe86B6 powders had also been studied. The results showed that Nd2Fe14B grain refined quickly and the grain size of α-Fe decreased while extending milling time. After milling for 25h, grain size of α-Fe reached a constant (about 7nm). Higher temperature of complete crystallization as well as finer and more homogeneous grains resulted from longer milling time. During the process of crystallization, the total amorphous phase crystallized into four phases firstly, i.e., Nd4.4Fe77.8B17.8, Nd1.1Fe4B4, Nd2Fe14B and α-Fe. At higher temperature, final mixture was consisted of Nd2Fe14B, α-Fe and a few undecomposed Nd1.1Fe4B4 phase.

Effect of Mechanical Milling and Cold Pressing on Co Powder

Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at 615C°. Upon annealing at 700C°, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at 615C° corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase with a=3.80 Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parameters a=b=3.80 and c=3.07 Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameter a shrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at 750C°, the FCT to FCC transition occurred, yielding the FCC phase with a=3.51 Å.

Effects of mechanical milling on preparation and properties of CuAl1−xFexO2 thermoelectric ceramics

CuAl1−xFexO2 (x=0, 0.1, and 0.2) thermoelectric ceramics produced by a reaction-sintering process were investigated. Pure CuAlO2 and CuAl0.9Fe0.1O2 were obtained. Minor CuAl2O4 phase formed in CuAl0.8Fe0.2O2. Addition of 10mol% Fe lowered the sintering temperature obviously and enhanced the grain growth. At x=0.1, electrical conductivity=3.143Ω−1cm−1, Seebeck coefficient=418μVK−1, and power factor=5.49×10−5Wm−1K−2 at 600°C were obtained. The reaction-sintering process is simple and effective in preparing CuAlO2 and CuAl0.9Fe0.1O2 thermoelectric ceramics for applications at high temperatures.

Lithium Ion Storage Characteristics of Mechanically Fractured Titanate Nanotubes

The effect of mechanical milling on the formation of short titanate nanotube and structural change induced is investigated. Mechanical milling produces the short nanotubes with the length of 30–160 nm. The lithium ion intercalation characteristics of the obtained short titanate nanotube were studied to verify the effect of the newly formed cross‐sections of nanotubes. It was found that the protonated titanate nanotubes maintained long shapes until 30 min of mechanical milling and were transformed into agglomerated nanosheets and finally anatase granules depending on the treatment duration. Through galvanostatic investigation, the nanotubes with milling of 15 min exhibited the highest discharge capacity of 336 mAh·g−1 in first cycle, 12.4% larger than pristine.

Effect of Mechanical Milling on the Thermal Behavior of Polyethylene Reinforced with Nano-sized Alumina

Abstract In the current study the dependency of morphology and thermal behavior of medium density polyethylene (MDPE) powder reinforced with 0, 5, 10 and 15 wt.% nano-sized Al2O3 particles on mechanical milling were studied. The effects of milling time on the morphology and the thermal behavior were investigated by Transition Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Differential Scanning Calorimetery (DSC) and Thermo Gravimetric Analyzer (TGA). The TEM micrographs obtained from the nanocomposites proved that mechanical milling could be an adequate method to disperse nano-sized hard particles throughout the polymer. The SEM micrographs of pure MDPE showed that regular shape powder converted to the flake shapes as milling time increased. Also the results illustrated that an increase in milling time caused to decrease the agglomeration of alumina. The DSC profiles of samples elucidated that ball milling had little effect on crystalline temperature and melting point of all materials including MDPE and its nanocomposites. The nanocomposite exhibited more thermal stability than pure polyethylene proved by TGA tests.