Effect Of Mechanical Milling Research Articles

Effect of mechanical milling on microstructure evolution and mechanical properties of Al–Zn–Mg–Cu–Si alloy fabricated via spark plasma sintering

We investigated the effect of high-energy ball milling (HEBM) on the microstructure and mechanical properties of powders and spark plasma sintered samples of an Al–Zn–Mg–Cu–Si alloy. HEBM produced a nanocrystalline powder with an average grain size of 0.16 μm while increasing the amount of solid solution and the formation of fine amorphous aluminium oxide. The sintered alloy without HEBM consisted of η-Mg(Zn,Cu,Al)2, T-Mg32(Al,Zn)49, β-Mg2Si, and Q-Al5Cu2Mg8Si6 phases. The grain size of the sintered alloy decreased from 2.66 to 0.40 μm due to the application of HEBM. The amorphous aluminium oxide phase in the milled powder was transformed into MgO particles during sintering. The formation of MgO particles caused the depletion of Mg solid solutions, which resulted in the formation of Mg-free phases during sintering. High-energy ball milling (HEBM) improved the microhardness of the sintered alloy from 94 to 134 HV owing to grain refinement and the formation of fine secondary phases and MgO particles.

Effects of Mechanical Milling and FAST Sintering on Mg Powders: Microstructural Analysis and Mechanical Properties

This study investigates the sintering mechanism of commercially pure Magnesium (Mg) using the Field Assisted Sintering Technique (FAST). FSEM and XRD analysis identified four distinct bonding and sintering mechanisms influenced by particle geometry, residual stress, and microstructure developed through mechanical milling. XRD analysis demonstrated variations in crystallite size and lattice micro-strain with increasing milling time. The combination of mechanical milling and FAST exhibited significant effects on the microstructural and mechanical properties of Mg powders, with the Mg36 sample displaying promising strength and hardness.

Effect of mechanical milling on powder characteristics of Fe-based metal matrix composites reinforced with WC–Co and NbC particles

Effect of mechanical milling on powder characteristics of Fe-based metal matrix composites reinforced with WC–Co and NbC particles

Influence of mechanochemical activation on the thermal behavior of pyrophyllite

The effect of mechanical milling on the thermal behavior of pyrophyllite ore from a deposit in Parsovici, Bosnia and Herzegovina, was characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and Particle size distribution. The thermal behavior of the material was followed by thermogravimetric and differential thermal analysis and correlated to its microstructural properties. The Williamson-Hall model was used to calculate the crystallite size and microstrain. Mechanochemical treatment of pyrophyllite ore produced a substantial structural modification, mainly along the c axis, resulting in disorder and partial degradation of the crystal structure of the ore. The particle size diminution, induced defects, and microstrain in the crystal lattice cause decrease in the peak intensity until the final disappearance. As confirmed by scanning electron microscopy and particle-size-distribution analysis, the surface area and the agglomeration is more pronounced as grinding time increases. Dehydroxylation of the minerals in the unmilled ore was realized at 716oC confirm by FTIR analysis. The endothermic peak that corresponds to dehydroxylation is shifted toward lower temperatures and becomes broad giving rise to the formation of amorphous SiO2 as milling time increases.

Effect of mechanical milling and sintering on magnetic entropy of Ni-based Ni2CuCrFeAl x (x = 0.5, 1.0, 1.5 and 2.5) high entropy alloys

ABSTRACT Nickel-based Ni2CuCrFeAl x (x = 0.5, 1.0, 1.5 and 2.5) high-entropy alloys with good magneto-caloric properties have been successfully prepared by a mechanical milling technique. The phase transformation from FM to PM at the transition point was linear with composition and T c, respectively. Substitution of Al by mechanical milling with subsequent sintering induces a tetragonal distortion in the BCC structure. Prolonged hours of milling followed by sintering result in an increase in magnetic entropy that may result in high refrigeration capacity (RC). Temperature-dependent isothermal magnetization exhibits second-order magnetic phase transition with varying temperature. Moreover, it could be envisaged that distortion occurs in the alloy not only due to the milling effect, but sintering also plays a vital role in achieving large magnetic entropy due to the formation of different intermetallics. This study shows the variation in magnetic entropy of the alloy prepared by mechanical milling followed by sintering at 1073 K.

Effect of mechanical milling on magnetic, dielectric and magneto-electric properties of Z- type (Ba, Sr) hexaferrites

The Z-type hexaferrites Sr3Co2Fe24O41 (SCFO) and Ba3Co2Fe24O41 (BCFO) were prepared via sol-gel method and were ball milled for different duration to study the effects of reduction in particle on the physical properties of these compounds. The phase formation was confirmed by using X-ray diffraction (XRD) whereas Scanning Electron Microscopy (SEM) was employed to analyze the surface morphologies of these samples. Magnetization measurements i.e. (M-H) at room temperature were performed by using Vibrating Sample Magnetometer (VSM) and it is observed that the magnetic coercive field (Hc) has increased with reduction in particle of the samples i.e., with ball milling. Magneto electric effects of (Ba, Sr) Z-type hexaferrites at room temperature were measured indirectly by examining the change in polarization (P-E loop) with and without magnetic field. It is evident from P-E loops of SCFO that magnetic field affects the electric polarization for all ball-milled samples and it is an indication of ME coupling in these samples at room temperature.

Effect of mechanical milling on structural and photocatalytic properties of chemically synthesized ZnSnO3nanopowder

In this work, we report the structural and photocatalytic properties of chemically synthesized unmilled (0 hr) and mechanically milled (0.5 hr and 2 hrs.) ZnSnO3nano-powder. Samples were calcined at 700 °C after synthesis. Prepared samples were characterized by XRD, FESEM, EDX and UV–Vis spectroscopy. Rietveld refinement of x-ray diffraction was employed for microstructural analysis and this confirms successful synthesis of pure, single phase orthorhombic ZnSnO3 with space group Pnma. Grain size was also evaluated from FE-SEM micrographs using Image-J software. It was noticed that the optical band gap value (analyzed by UV–Vis spectroscopy) of the milled sample is greater than the unmilled sample indicating quantum confinement effect. Photocatalytic activity of ZnSnO3 catalysts was investigated using a model organic pollutant Congo red under visible light irradiation. Milled ZnSnO3 catalyst with lower grain size showed superior photocatalytic property in our studies. Attempt was made to correlate photocatalytic properties with variation of grain size and microstrain of the unmilled and milled sample.

Combined Mössbauer Spectrometry and Atom Probe Tomography Investigation of Mechanically Milled Rare Earth / Transition Metal Powders

"The microstructure of mechanically milled Nd2Fe14B, SmCo5/Fe and SmCo3Cu2/-Fe alloys has been investigated by Mössbauer spectrometry and atom probe tomography. The structural changes that occur upon milling and subsequent annealing were characterised at a nanometer scale. Milling promotes intermixing of the elements and the formation of nanograins. In Nd-Fe-B powders, the Nd2Fe14B phase is transformed into -Fe and an amorphous Nd-Fe-B phase. In SmCo5/Fe powders, Fe/Co intermixing occurs, leading to the formation of Sm(Co,Fe)5 and -Fe(Co) phases. In SmCo3Cu2/Fe powders, although Sm is partly oxidised, Fe/Co intermixing occurs as well, leading to the formation of -Fe(Co) nanograins surrounded by Sm(Co,Cu,Fe)5 intergranular regions. The combined Mössbauer and atom probe tomography investigation of rare earth / transition metal powders thus allows revealing the effect of mechanical milling and subsequent annealing on the nanostructure of the powders. These results are helpful for the understanding of the magnetic properties of the powders. Keywords: rare earths-transition metals powders, Mössbauer spectrometry, atom probe tomography "

Effect of mechanical milling on lithium-ion conductivity of LiAlH4

The effect of mechanical milling on the lithium-ion conductivity of lithium alanate (LiAlH4) is investigated. Although pristine LiAlH4 is a poor ion conductor in its highly crystalline state, short-time mechanical milling for 0.1–2 h is shown to significantly improve the conductivity. Hand-milling treatment in an argon-filled glove box is also shown to improve the conductivity. The activation energy (Ea) for ion conduction of milled LiAlH4 is ~0.70 eV, which is attributed to Li-ion site vacancy-mediated conduction. However, the Ea of pristine LiAlH4 shows a large value of 0.84 eV. The 7Li, 6Li, 27Al nuclear magnetic resonance and infrared spectra suggest that surface Li hydroxide species would exhibit Li-ion conduction in pristine LiAlH4. Thus, the milling treatment can eliminate the effect of surface hydroxide species and increase the vacancy concentration at the Li-ion site of inner LiAlH4 grains, which results in the enhancement of the conductivity.

Effect of mechanical milling on the harmonic structure development during spark plasma sintering of Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe β-metastable titanium alloy (β-Cez alloy)

The present study focuses on the formation of harmonic microstructures in a metastable β titanium alloy, the β-Cez alloy (Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe – Tβ = 895 °C). Previous studies emphasized mainly fabrication and improvements in the mechanical properties of alloys prepared by powder metallurgy and showing a harmonic structure. In this study, the harmonic structure was obtained after mechanical milling of the initial powder, followed by a Spark Plasma Sintering (SPS) process. During the process, phase transformations occur that are dependent on the initial state of the powder. Moreover, their kinetics depend on the thermo-mechanical history of the powder. In order to analyze the microstructure formation, the behavior of milled and non-milled powders was studied during a heat treatment similar to the one applied during the SPS process. In-situ high-energy X-ray diffraction was used to characterize the evolution of phases during the thermal treatment. Additional in situ electrical resistivity measurements were carried out on sintered compact specimens. Characterizations evidenced that the initial powder is in a β metastable state. After mechanical milling, stress/strain induced α” martensite was observed inside the powder’s β grains. The stepwise microstructural characterization revealed the influence of the initial state of the mechanically milled powder on the formation of a harmonic α arrangement in the β matrix consisting of nodular α grains in the powder shell and α lamellae in the powder core. The stress/strain induced martensite formed during the milling associated with the heavier deformation at the powder surface areas contributes highly to the formation of an arrangement of nodular α grains by a recovery/recrystallization phenomenon of β and α”/α phases during the heating.

Effect of Mechanical Milling on the Mechanical, Dry Sliding Wear, and Impact Response of Sintered Nickel Based Superalloy

In this study, effect of mechanical milling on the mechanical, dry sliding wear and impact response of spark plasma sintered Ni-17Cr6.5Co1.2Mo6Al4W7.6Ta superalloy has been investigated. Two nickel-based superalloy were sintered, firstly in their as-received elemental particle sizes, while the matrix, nickel of the second alloy, was milled to 10 h prior blending with other elements and subsequent sintering. The impact response was explored using computational modelling approach via finite element analysis, Abaqus CAE/2019. Results show that the superalloy with the milled nickel powder exhibited better mechanical properties such hardness, elastic modulus, elastic and plastic strain from impact response than the superalloys with unmilled nickel. Sliding wear tests under dry sliding conditions at three different loads of 20, 25 and 30 N revealed that the superalloy with the milled nickel have lower wear rate when compared to the other with unmilled nickel. It was observed that the wear rate reduced unexpectedly at the applied load of 30 N which may be attributed to the continuous formation of tribo-oxide layer from retained wear debris on worn surface.

Influence of mechanical milling on the hydrogen absorption properties of TiCrV – based alloys

The hydrogen economy is a concept focused on this element as a carrier of clean and cheap energy, one of the keys is the storage of this gas safely. In this sense, TiCrV-based alloys have great capacity to store hydrogen. In the present working studied the influence of the process of mechanical milling of high energy in the storage capacity of hydrogen of TiCr1.1 V0.9 alloy. The alloy was synthesized by arc fusion and manually crushed. The effects of mechanical milling were studied for periods of time of 1 hour and 3 hours at 300 revolutions per minute with a weight/weight ratio of the sample 10: 1. The x-ray diffraction analyzes revealed solid phase formation of body center cubic phase, characteristic of TiCrV base alloys, and formation of TiCr1.8H5.3 hydrides and TiH2 hydrides with orthorhombic structure and body center cubic, respectively. The hydrogen storage capacity of the TiCr1.1 V0.9 alloy decreased with the increase in grinding time. The reasons for the drop in hydrogen storage capacity are mainly two: contamination of the surface of the alloy powder and changes in the microstructure generated by the plastic deformation in the grinding process. However, an increase in absorption kinetics was observed at longer milling times because the surface area increases since the crystallite size decreases. This phenomenon can be explained by the catalytic effect produced by the decrease in the particle size of the samples. The differential scanning calorimetry analysis was able to determine that the TiCr1.8H5.3 hydride stored a greater amount of hydrogen and has a lower desorption temperature compared to the TiH2 hydride.

Microstructure and Mechanical Properties of Copper-Iron Fabricated by Mechanical Milling and Continuous Sintering

This research is to analyze the effect of mechanical milling on the microstructure and mechanical properties of copper-iron. The sample is fabricated by compacting, milling and sintering processes. Sintering process is carried out using continuous type machine with conveyor belt mesh and the furnace type is muffle. After that, it is cooled with natural water jacket process. Vicker hardness testing and tensile strength test is performed to determine the mechanical properties of copper-iron alloys that occur. The mean value of sample 1 hardness (before milling) was 39.8 HV. The mean value of sample hardness 2 (after milling) was 74.9 HV. The value of the yield strength (σ) of sample 1 is 17.597MPa, and the value of ductility (ε) is 0.119. The value of the yield strength (σ) of sample 2 is 18.547 MPa, and the value of ductility (ε) is 0.073. The test results and analysis showed that by shrinking the size of metal powder, by milling for 2 hours, the hardness and yield strength of the product can increase. Although, the product becomes more brittle which is indicated by the decreased ductility value.

Study on powder preparation of IGZO target and its effect on sintering

In this study, the powder preparation process of indium–gallium–zinc oxide (IGZO) and its effect on sintering were investigated to develop high-quality IGZO ceramic material as sputtering target. The effects of mechanical milling on the morphology, phase, size distribution and specific surface area of IGZO mixture particles were studied. Furthermore, the optimized powder states for sintered IGZO ceramics were analyzed. The results showed that the IGZO mixture particles were refined and the size difference between particles was significantly decreased after milling for 45 h. Moreover, the uniformity, size distribution and specific surface area of IGZO mixed powder were greatly improved. The pressed powders showed regular morphology, without any cracking or deformation. Three critical factors of powder treatment were identified which controlled the quality of the sintered IGZO target. Finally, using the optimized conditions, IGZO target was obtained with high density (relative density > 99%), regular shape, homogeneous microstructure (grain and element distribution) and controlled phases.

Thermomechanical synthesis of hybrid in-situ Al-(Al3Ti+Al2O3) composites through nanoscale Al-Al2TiO5 reactive system

In this work, nanostructured aluminum titanate (Al2TiO5 or AT) was synthesized by the citrate sol gel method. Then, different volume fractions of this ceramic were blended with Al powder through different durations of the high-energy vibratory milling. The effect of mechanical milling on the thermal degradation of AT in exposure to Al and formation mechanism of in-situ Al2O3 and Al3Ti particles were explored in three conditions: (i) in the powder form; (ii) after annealing of green compact; and (iii) after hot extrusion. In the powder form, it was shown that the mechanical milling is able to significantly diminish the thermal stability of AT, so that the required temperature for the Al3Ti formation decreases from 600 to about 450 °C. Also, by extending the mechanical milling duration, the contact surface for interfacial reactions between Al and AT increases and the formation of Al3Ti and Al2O3 is facilitated. By selecting the optimum duration of mechanical milling, this study successfully fixed the microstructure problems of not-milled as-annealed composites i.e. unreacted AT particles and oxygen evolution-arisen cracks, and produced in-situ composite inside each Al particle. However, the induced work hardening of these milled particles hinders the perfect consolidation. To deal with this challenge, the hot extrusion at 535 °C was conducted. The obtained microstructure was composed of very fine (≤200 nm) semi-spherical Al3Ti and Al2O3 particles uniformly distributed within the Al matrix. To evaluate the mechanical response of the fabricated nanocomposites, the micro-hardness and nanoindentation testing were carried out. The results proved that the hardness and elastic modulus of the nanocomposites reach 143 HV and 90 GPa, respectively, indicating a significant improvement in the mechanical properties of these systems compared to not-milled extruded composites. Finally, the role of reinforcing particles in strengthening of composite was evaluated.

Milling effect on the microstructural and hydrogenation properties of TiFe0.9Mn0.1 alloy

TiFe is a remarkable hydrogen storage alloy thanks to its reversibility at ambient temperature and pressure, high capacity and low cost. However, activation and sorption kinetics should be improved for practical applications. The effect of mechanical milling on the morphological, structural and hydrogen sorption properties of powdered TiFe0.9Mn0.1 alloy has been determined. Pristine alloy powder with mean particle and crystal sizes of 45 μm and 30 nm, respectively, was used as a reference. The pristine powder was ball milled for different times up to 5 h leading to significant changes in microstructural properties already observed after 0.5 h of milling. For such short milling time, the particle and crystal sizes decrease by a factor of five and three, respectively, with minor formation, if any, of amorphous phases. These microstructural changes promote a reduction of the activation time towards hydrogen absorption by a factor of five and enhance sorption kinetics. Besides, the hydrogen thermodynamic properties are slightly modified leading to sloping plateau pressures and hydride stabilization. These modifications may lead to a lowering of apparent desorption rates which should be carefully considered for the use of milled TiFe-type alloys in practical applications.

The oxidation kinetic study of mechanically milled ultrafine iron powders by thermogravimetric analysis

The effect of mechanical milling on the oxidation kinetics of ultrafine iron powders was investigated by thermogravimetric (TG) analysis. The initial α-Fe powder with average particles size of 100 nm was made by the electric explosion of wire. The milling of iron powder was carried out by AGO-2S planetary ball mill using a rotation speed of 2220 rpm and the milling times of 15 and 40 min. According to the XRD data, the main content of α-Fe was observed in all samples. However, a certain amount (~ 20 mass%) of wustite phase (FeO) is formed after ball milling of ultrafine iron powders. From TG analysis, the powders milling leads to increase in the temperature of thermal oxidation onset and shifts the reaction to higher temperatures. A model-free isoconversional method of the Friedman analysis was employed only in a first qualitative approximation. More accurate kinetics parameters were obtained using the multivariate nonlinear regressions, where three-step reaction with branching set of n-order equations for each step was chosen.

The Mechanical Properties and In Vitro Biocompatibility of PM-Fabricated Ti-28Nb-35.4Zr Alloy for Orthopedic Implant Applications.

A biocompatible Ti-28Nb-35.4Zr alloy used as bone implant was fabricated through the powder metallurgy process. The effects of mechanical milling and sintering temperatures on the microstructure and mechanical properties were investigated systematically, before in vitro biocompatibility of full dense Ti-28Nb-35.4Zr alloy was evaluated by cytotoxicity tests. The results show that the mechanical milling and sintering temperatures have significantly effects on the density and mechanical properties of the alloys. The relative density of the alloy fabricated by the atomized powders at 1500 °C is only 83 ± 1.8%, while the relative density of the alloy fabricated by the ball-milled powders can rapidly reach at 96.4 ± 1.3% at 1500 °C. When the temperature was increased to 1550 °C, the alloy fabricated by ball-milled powders achieve full density (relative density is 98.1 ± 1.2%). The PM-fabricated Ti-28Nb-35.4Zr alloy by ball-milled powders at 1550 °C can achieve a wide range of mechanical properties, with a compressive yield strength of 1058 ± 35.1 MPa, elastic modulus of 50.8 ± 3.9 GPa, and hardness of 65.8 ± 1.5 HRA. The in vitro cytotoxicity test suggests that the PM-fabricated Ti-28Nb-35.4Zr alloy by ball-milled powders at 1550 °C has no adverse effects on MC3T3-E1 cells with cytotoxicity ranking of 0 grade, which is nearly close to ELI Ti-6Al-4V or CP Ti. These properties and the net-shape manufacturability makes PM-fabricated Ti-28Nb-35.4Zr alloy a low-cost, highly-biocompatible, Ti-based biomedical alloy.

Synthesis and characterisation of submicron silica particles from rice husk

Rice husk is considered an important silica source. In this work, microsilica particles were obtained by incineration of rice husk and milling of its ash. The synthesis process was carried out by incinerating the rice husk at 700°C, followed by acid leaching in order to remove inorganic impurities and finally mechanical ball milling at 0, 18, 36 and 72 h to reduce the particle size. Thermogravimetric analysis shows the thermal degradation of rice husk and elimination of organic components. The chemical composition was studied by X-ray fluorescence. The structural properties of silica were determined by X-ray diffraction. The morphological changes caused by mechanical milling were studied by scanning electron microscopy (SEM). The results indicate that between 150 and 450°C, the organic material of the husk was released, and above 550°C, ash with high silica content was obtained. Acid leaching increased the silica purity from 93·40 to 98·22%. According to the X-ray diffraction analysis, the predominant phase was silica. The reduction in the crystallinity of silica samples was shown as an effect of mechanical milling while the particle size was reduced. The percentage of crystallinity decreased from 33·5 to 28·5% for after 72 h of milling. The SEM images showed that the particle size reduced with an increase in milling time, obtaining particle diameters smaller than 2·0 μm. The amorphous silica obtained from rice husk can be used for the production of high-performance silicon, silicon carbide, silicon nitride, silicon tetrachloride and zeolites.

Effect of mechanical milling of fly ash on friction and wear response of brake friction composites

The effect of milled fly ash on the tribological response of brake friction composites is studied. Two specimens were developed using raw fly ash (RFA) and milled fly ash (MFA) and tested for the friction and wear performance at different loads (50-100 N) with sliding velocities varying from 1.7 to 3.3 m/s. It was observed that the spherically shaped RFA particles transformed into rough and uneven shaped particles after ball milling. The particle size range was found to be 22.05-206.19 μm before milling which reduced to 3.02-40.64 μm after milling while the specific surface area increased from 138.23 m2/m3 to 1008.98 m2/m3. The μavg of RFA specimen varied from 0.23 to 0.57 during braking conditions. However, the MFA specimen experienced approximately a constant value of 0.52 at 50 N with the increase in sliding velocities, whereas slight variation was observed at higher loads. The results showed that the mechanical milling enhances the stability and consistency of friction coefficient as compared to raw fly ash.