Initial Stage Of Milling Research Articles

Glass-Forming Ability and Magnetic Properties of Al82Fe16Ce2 and Al82Fe14Mn2Ce2 Alloys Prepared by Mechanical Alloying

Al82Fe16Ce2 and Al82Fe14Mn2Ce2 amorphous alloys were successfully synthesized by the mechanical alloying technique. The microstructural evolution of the milled powders was thoroughly investigated employing X-ray diffraction (XRD) and scanning electron microscopy (SEM). Additionally, their magnetic properties were quantitatively evaluated by a vibrating sample magnetometer (VSM). A full amorphous structure was obtained for both alloys after milling for 40 h. During the initial milling stage, extending from 5 to 20 h, an fcc solid solution phase was formed, coexisting with the residual Al phase. The partial substitution of 2 atomic percent (at.%) Mn for Fe in Al82Fe16Ce2 did not affect the alloy’s glass-forming ability. The amorphous Al82Fe16Ce2 and Al82Fe14Mn2Ce2 powders exhibited a nearly spherical shape, with diameters ranging from 1 to 3 µm and to 10 µm, respectively. Additionally, both the Al82Fe16Ce2 and Al82Fe14Mn2Ce2 alloys demonstrated characteristics of hard magnetism.

Study of the ball milling condition effect on physicochemical and structural characteristics of wheat flour

An investigation of the changes in the properties of starch due to mechanical and thermal effects was taken. The milling temperature and time were strictly controlled, and the particle size, relative crystallinity, damaged starch content, pasting characteristics, and thermal properties of the ground sample from different feed sizes were determined. The results showed that the feed particle size had a significant influence on the particle size distribution, peak viscosity, and final viscosity of the milled product at the initial milling stage. Minimum feed particle size (3.75 ~ 623 μm) flour has the largest peak viscosity (2,881.5 ± 58.7 cP & 2,895.0 ± 38.2 cP) after milling 15 min. The sieving results showed that better breakage effect for coarser particle size after same milling time, particularly under normal temperature. The data of relative crystallinity indicating that keeping a lower temperature range (<25℃) during the milling process may be beneficial to the protection of the starch crystallization. In addition, the difference of thermal properties of the milled products may be caused by the different degrees of starch exposure in endosperm granules and the change of surface protein properties during milling. Novelty impact statement The feed particle size has a significant effect on the peak and final viscosities of the short-time ball milling flour. Cryo-milling can protect the relative crystallinity of wheat granules. The degree of starch granule exposure affects the impact of mechanical force during milling.

Manufacturing of TiC-Cu composites by mechanical milling and spark plasma sintering using different carbon sources

In this article, the features of the in-situ synthesis, microstructure evolution and mechanical properties of TiC-Cu composites obtained by mechanical milling and spark plasma sintering (SPS) are presented. The goal of this work is to study the effect of the carbon source on the microstructure evolution during the manufacturing of TiC-Cu composites from Ti-C-3Cu mixtures. Graphite, nanodiamonds and carbon black powders are compared as the carbon sources in the synthesis in terms of their influence on the structural evolution of the composite mixtures. In the case of graphite, mixing and alloying are retarded at the initial stages of milling. The use of carbon black and nanodiamonds ensures faster conversion of the reactants into the products during milling compared with graphite, as concluded from the studies of thermal explosion of those mixtures. Irrespective of the source of carbon, melting is observed at the contacts between equiaxed particles in the materials consolidated by SPS leading to the formation of composites with an interesting (unconventional) microstructure. The compressive yield strength, ultimate compressive strength and hardness of selected TiC-Cu composites are reported. A TiC-Cu composite with an attractive combination of properties has been obtained (processing conditions: Ti-Cgraphite-3Cu mixture, 10 min of milling, SPS at 980°C): a relative density of 95%, a compressive yield strength of 820 MPa, an ultimate compressive strength of 920 MPa, a hardness of 360 HV, a deformation at fracture of 2%, and an electrical conductivity of 18% of the International Annealed Copper Standard.

Study on tool wear mechanism and cutting performance in helical milling of CFRP with stepped bi-directional milling cutters

Helical milling, a new machining technology, has obvious advantages in hole making of carbon fiber reinforced plastic (CFRP), and the technology, nonetheless, shows some defects such as hole diameter tolerance and surface damage aggravation caused by fast tool wear. Aiming to improve the hole making quality of CFRP, this paper proposes the bi-directional helical milling strategy, carries out the experimental research on milling CFRP with stepped bi-directional milling cutters, analyzes the wear mechanism of forward and backward cutting edges, and thus obtains the change laws of cutting forces and hole-making quality in different tool wear conditions. The experimental results show that in the initial milling stage, strip-shaped and spoon-shaped wear bands are formed by abrasive wear mechanism on both forward and backward cutting edges; with aggravation of the tool wear, the wear mechanism of forward cutting edge is gradually dominated by the fatigue wear, and subsequently, a large-area coating peels off the tool surface, causing the rapid wear of substrate. Compared with the forward cutting edge, the backward cutting edge produces less and more stable axial cutting force, and causes all the cutting forces to rise more slowly. In comparison with traditional drilling and milling of CFRP, bi-directional hole-making can effectively suppress some defects such as hole diameter shrinking, burrs and tearing, and thus it shows better machining quality.

Effect of Powder Morphology and Chemical Distribution on Properties of Multicomponent Alloys Produced Via Powder Metallurgy

In this study, effects of morphology and chemical distribution of powder on mechanical properties was investigated in Al0.5CoCrCuFeNi high-entropy alloys produced via powder metallurgy. At the early stages of ball-milling, Cr-deficient large powder is flattened, while Cr-rich powder is fractured to small particles because of the flattening of ductile particles and fragmentation of hard particles at initial milling stage. However, with an increase in the milling duration, the Cr atoms were more uniformly distributed throughout the powders and the powders exhibited spherical shape with smooth surface. Moreover, as the ball-milling duration increased from 36 to 96 h, the Vickers hardness and compressive yield strength also increased from 433 Hv0.5 and 1166 MPa to 525 Hv0.5 and 1739 MPa, respectively. This was attributed to the spherical powders reducing as well as forming fine and uniform microstructures in sintered alloys. Also, the elemental uniformity suppressed the formation of dendritic-unfavorable carbides.

Reaction kinetics of fly ash geopolymerization: Role of particle size controlled by using ball mill

Fly ash is milled for 0, 30 and 90 min and used to study the role of particle size on the kinetics of geopolymer formation. The increase in particle fineness is very prominent in the initial milling stage, and then slows down due to agglomeration effect of finer fraction. The fly ash geopolymerization kinetics and its mechanism is determined using heat of reaction data measured by isothermal conduction calorimeter. The improvement in reaction rate with milling is correlated with the median particle size of the fly ash. The apparent activation energy decreases with size reduction because finer fractions are more prone to alkali activation. Although the kinetics changes with particle fineness, but no alternation is detected in the reaction mechanism, governed by nucleation and growth. The apparent activation energy evaluated by rate method is showing three major steps of geopolymerization such as dissolution, gel formation and restructuring.

Two-stage ball milling of recycled machining chips to create an alternative feedstock powder for metal additive manufacturing

To explore alternative and sustainable feedstock production for metal additive manufacturing, stainless steel powders were fabricated from recycled machining chips by ball milling. To achieve the desirable powder characteristics for additive manufacturing, the effect of ball size on the powder morphology change and particle size reduction was investigated through both theoretical analysis on the maximum deformation depth in the powder during ball milling and extensive experimental work. The modeling results suggest that large balls (diameter = 20 mm) efficiently break up machining chips to coarse powder particles while small balls (diameter = 6 mm) effectively modify the powder morphology to near-spherical. Therefore, a two-stage ball milling approach, i.e., using large balls at the initial stage of milling followed by a second stage of milling with small balls, was proposed in experiments and successfully converted machining chips to powders with near-spherical shape and particle sizes ranged from 38 to 150 μm. In addition, the nanoindentation hardness of the ball milled powder created from machining chips is 56% higher than the gas atomized powder. To verify the usability of the ball milled powder created from recycled machining chips in additive manufacturing, single tracks have been successfully deposited via laser engineered net shaping.

Evolution of metal nitriding and hydriding reactions during ammonia plasma-assisted ball milling

Nanocrystalline metal nitride and hydride powders were prepared using plasma-assisted ball milling in ammonia gas (NH3-P-milling) via an in situ synthesis reaction. The gas–solid reactions were triggered by a short duration of plasma milling of Mg and Ti under a constant pressure of ammonia gas, and the products in the two systems were nanocrystalline Mg3N2 and TiN, TiH2 after 10 h, respectively. During the NH3-P-milling of Ti powder, TiH2 and TiN were formed during the initial stages of milling, and then, the TiH2 decomposed during further milling upon reaction with N radicals, transforming into the TiN phase. In contrast, no chemical reaction occurred between NH3 and Mg/Ti after 10 h of C-milling. The discharge plasma activated and decomposed the ammonia gas and activated the surface of the powders, which, together with the mechanical effect of high-energy ball milling, accelerated the gas–solid reactions.

Influence on the structural and magnetic properties of pre-alloyed gas-atomized Fe49Co49V2 powders during mechanical milling

The influence on the structural and magnetic properties of pre-alloyed gas-atomized Fe49Co49V2 powders during mechanical milling was investigated. The powders were mechanically milled for up to 45 h. The powders, before milling, were principally comprised of α-phase. No noticeable phase transformation was observed during mechanical milling of the pre-alloyed powders. Mechanical milling resulted in a gradual decrease in crystallite size to as low as ~10 nm, accompanied by an increase in lattice strain to ~1.2–1.5%. Mechanical milling led to an appreciable reduction in the particle size while the morphology of the milled powders appeared similar once the steady-state was attained. The lattice parameter of the nanostructured powders at steady-state was estimated as 0.2857 ± 0.0004 nm. The saturation magnetization (MS) of the nanostructured powders milled for ~45 h was ~211 ± 1 Am2/kg, and it decreased only by ~6% compared to that of the pre-alloyed gas-atomized powders before mechanical milling. The intrinsic coercivity (HCI) of the pre-alloyed powders was estimated as ~1.4 ± 1% kA/m. The HCI peaked to ~8.4 kA/m during the initial stages of milling and subsequently remained between ~6.5 kA/m to ~6 kA/m, during the later stages of milling. As would be expected, the HCI was strongly dependent on the crystallite size. The ferromagnetic exchange length of the nanostructured powders was estimated to be ~27 nm. The magnetic properties of nanostructured Fe49Co49V2 powders obtained by mechanical milling of pre-alloyed powders had relatively superior magnetic properties compared to the nanostructured powder obtained by mechanical alloying of the constituent elemental powders.

Influence of Mechanical Alloying Time on Morphology and Properties of 15Cr-ODS Steel Powders

Abstract Oxide dispersion strengthened (ODS) ferritic steels are the leading candidates of fuel cladding for Generation IV nuclear reactors due to their excellent properties such as excellent radiation tolerance and high-temperature creep strength. Mechanical milling with the aim of a fine dispersion of oxides in the metal matrix becomes the main process for the production of ODS steels. In order to clarify the influence of milling time on the precursor powders for 15Cr-ODS steel, the morphology and properties of mechanical alloying (MA) powders with different milling time were investigated by scanning electron microscopy (SEM), laser diffraction particle size analyzer, X-ray diffraction (XRD) and Vickers hardness tester. The experimental results showed that the powder was fractured and welded with rotation and vibration of container during mechanical milling. The mean powder size increased (0–1 h) firstly then decreased (2–60 h). Extending milling time to 70 h, the mean powder size increased again. The grain size decreased quickly at the initial stage of milling process (0–2 h) then trended to reach a saturation value. The Vickers hardness increased rapidly at the initial stage of milling, then reached a saturation value.

Cutting Temperature Behaviours in End Milling of Pocket by Applying Contour-In Tool Path Strategy

Cutting temperature generated during high speed machining operations has been recognized as major factors influence tool performance and workpiece geometry. This paper aims to model the cutting temperature and to investigate cutting temperature behaviours when contour-in tool path strategy applied in high speed end milling process. The experiments were carried out on CNC vertical machining center by involving PVD coated carbide inserts. Cutting speed, feed rate and depth of cut were set to vary. Results obtained indicate that cutting temperature is high in the initial stage of milling and at the corners region or turning points region. Portion of radial width of cut with workpiece in combination with the abrupt change of the milling path direction occur particularly in acute internal corners of a pocket leads to rise of cutting temperature.

Influence of Milling Time on Morphology and Properties of Precursor Powders for 9Cr Oxide Dispersion Strengthened Steel

In order to clarify the influence of milling time on the atomized precursor powders for 9Cr-ODS (Oxide Dispersion Strengthened) steel, the morphology and microstructure of atomized powders and mechanical alloying (MA) powders with different milling time were investigated by scanning electron microscopy (SEM), laser diffraction particle size analyzer, X-ray diffraction (XRD) and Vickers-hardness tester. The experimental results showed that the atomized powders are spherical in shape with the particle size of ~ 47 μm and the grain size of ~ 2 μm. With the increase of MA time, the morphology of MA powders becomes from spherical to lamellar structure, then to equiaxed shape. The mean powder size increases firstly then decreases. The grain size decreases quickly at the initial stage of milling process (0-2 h) then trends to reach a saturation value. The Vickers-hardness increases rapidly at the initial stage of milling, then reaches a saturation value.

Effect of milling time on the structure, micro-hardness, and thermal behavior of amorphous/nanocrystalline TiNiCu shape memory alloys developed by mechanical alloying

In the present paper, the effect of milling process on the chemical composition, structure, microhardness, and thermal behavior of Ti–41Ni–9Cu compounds developed by mechanical alloying was evaluated. The structural characteristic of the alloyed powders was evaluated by X-ray diffraction (XRD). The chemical composition homogeneity and the powder morphology and size were studied by scanning electron microscopy coupled with electron dispersive X-ray spectroscopy. Moreover, the Vickers micro-indentation hardness of the powders milled for different milling times was determined. Finally, the thermal behavior of the as-milled powders was studied by differential scanning calorimetery. According to the results, at the initial stages of milling (typically 0–12h), the structure consisted of a Ni solid solution and amorphous phase, and by the milling evolution, nanocrystalline martensite (B19′) and austenite (B2) phases were initially formed from the initial materials and then from the amorphous phase. It was found that by the milling development, the composition uniformity is increased, the inter-layer thickness is reduced, and the powders microhardness is initially increased, then reduced, and afterward re-increased. It was also realized that the thermal behavior of the alloyed powders and the structure of heat treated samples is considerably affected by the milling time.

Preparing TiC coating on AISI D2 steel using mechanical milling technique

Abstract In the present study, ball milling was employed to coat titanium carbide (TiC) powder on AISI D2 steel specimens. During the milling, TiC powder adhered on the surface by a combination of mechanical deposition, wear, cold welding and fracturing processes. Structure of the coatings at various stages was studied by X-ray diffraction and scanning electron microscopy (SEM). Composition of the coatings was analyzed by energy dispersive X-ray spectroscopy. Their hardness was also measured. It was found that structural and morphological characteristics of the coatings were affected by milling time. With increasing the milling time from 5 to 20 h, average thickness of the coatings increased from 10 to 90 μm and, thereafter, it decreased, which indicated that, during the initial stages of milling, cold welding was prominent; but, on further milling, fracturing became the predominant phenomenon. It was also observed that substrate hardening enhanced hardness of the coatings. Scratch test was used to evaluate the coating adhesion in different conditions.

Magnetic and structural properties of nanostructured (Fe65Co35)100−xCrx (x = 0, 10) powders prepared by mechanical alloying process

This work focuses on the preparation of nanostructured (Fe65Co35)100−xCrx (x=0, 10) powders by mechanical alloying. The powders are milled for different milling times (up to 90h). Characterizations of the milled powders were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibratory sample magnetometer (VSM). It was observed that the formation of bcc-FeCo and bcc-FeCoCr phases were completely accomplished after 60 and 90h of milling, respectively. The grain size decreases and the microstrain increases with increasing the milling time. In the initial stages of milling (up to 15h) for the (Fe65Co35)90Cr10 powders, the saturation magnetization (Ms) decreased but further milling (up to 90h) increased the Ms. However, the trend for coercivity was different and three stages were observed. An initial increasing stage (up to 15h of milling), followed by a reducing middle stage (up to 60h of milling) and then again an increasing final stage (up to 90h milling). Besides, for the same milling time of 90h, the addition of 10at.% of Cr to Fe65Co35 powders leads to higher coercivity and lower saturation magnetization.

The effect of simultaneous addition of Si and Co on microstructure and magnetic properties of nanostructured iron prepared by mechanical alloying

The aim of present work is to study the effect of Si contents on structural and magnetic properties of nanostructured (Fe65Co35)100−xSix (x=0, 10 and 20) powders prepared by mechanical alloying. The structural and magnetic properties of the mechanically alloyed powders were investigated by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and a Vibration Sample Magnetometer (VSM). The resulting powders mainly consist of micron-sized particles with an average crystallite size of 18nm. Morphological observations indicate that the addition of Si to the alloys leads to finer particles. According to the XRD test results, by increasing the milling time and/or the Si content, the grain size decreases and the internal microstrain increases. The magnetic measurements indicate that the higher amount of Si leads to lower values of saturation magnetization. Besides, the results show that during initial stages of milling (up to 20h), the coercivity increases and then decreases by further milling. Increasing the Si content, increases the reduction rate of coercivity.

Self-nanoscaling in FeCo alloys prepared via severe plastic deformation

Nanocrystalline Fe100−xCox (x=20, 35, 50, 60) alloys have been prepared by mechanical alloying of Fe and Co powders via high energy ball milling. The alloy formation process and microstructure evolution of the samples have been investigated. Energy filtered transmission microscopy (EFTEM) observations revealed the strip formation of the Fe and Co phases at an initial stage of milling. The final grain size of the equiaxed grains in the obtained alloys reached 8nm upon milling for 20h. The saturation magnetization of the mixtures of Fe and Co increases with milling time, indicating an increasing homogeneity in composition and the phase formation. It is found that the saturation magnetization is also dependent on the Co content, which reaches the highest value of 240emu/g at Fe65Co35. The phase transformation of the as-prepared FeCo alloys was also studied using differential scanning calorimetry.

Disorder driven optical processes in nanocrystalline ZnO

A systematic study on the modification of optical properties in mechanically milled ZnO powder has been reported here. The average grain size of the powder becomes ∼20 nm within 4 h of milling. Fluctuations of average grain size have been noticed at the initial stage of milling (within 15 min). Changes in grain morphology with milling have also been noticed in scanning electron micrographs of the samples. Room temperature optical absorption data shows a systematic red shift of absorption band edge (∼3.25 eV). The band tail parameter (extracted from the optical absorption just below the band edge) follows a simple exponential relation with the inverse of the average grain size. Significant increase of the band tail parameter has been noticed at low grain size regime. It has been analyzed that high values of band tail parameter is a representative of V Zn– V O type divacancy clusters. Room temperature photoluminescence spectra show decrease (except for 120 min milling) of band edge emission intensity with increase of milling time. Subsequent decrease of sub-band edge emission is, however, less prominent. The variation of PL intensity ratio (intensity at band edge peak with that at 2.3 eV) follows simple exponential decrease with the increase of band tail parameter. This indeed shows that band edge emission in ZnO is related with the overall disorder in the system, not grain size induced only.

Effect of high energy ball milling on compressibility of nanostructured composite powder

Compressibility of a nanostructured Al–5AlN composite powder synthesised via high energy ball milling for various times was studied by means of a modified Heckel equation. Since workhardening and morphological changes take place by milling evolution, the compressibility was consequently affected. Strengthening of composite compacts was influenced by milling and compaction processes, i.e. strength of compacts increased at longer milling times and higher compaction pressures. It was found that, at the initial stages of milling and higher compaction pressures, the strengthening was mostly affected from compaction process, whereas the milling strengthening fraction was near to unity at lower compaction pressures as well as prolonged milling. Nevertheless, a sharp increase in milling strengthening fraction of unreinforced Al occurred at intermediate milling times. The rate of strengthening induced by milling raised at higher compaction pressures.

Strain-induced structural transformation of single-phase Al–Cu–Fe icosahedral quasicrystal during mechanical milling

A single-phase stable icosahedral quasicrystalline sample of high quality with the composition Al62.5Cu25Fe12.5 was produced by the spray forming technique. The material was further investigated by mechanical milling under an argon atmosphere to avoid oxidation during milling. At the initial stages of milling (within 5 h) a significant broadening of the diffraction peaks was observed, indicating a reduction of crystallite size and the introduction of lattice strain, which can be linked to phason strain of the quasilattice. Line broadening was noticed to increase with increasing milling time and in the material milled for longer time only a few broad diffraction peaks, which can be identified as a nanoscale bcc phase (i.e. disordered B2 phase, a ∼ 2.9 Å), were visible. At this stage the diffraction signals belonging to the quasicrystals were no longer observable, indicating a complete transformation of the quasicrystals into the bcc phase. Finally, the bcc phase formed during milling transformed back to the quasicrystalline phase during subsequent annealing treatment. The microhardness measured on the milled powders was found to decrease with increasing milling time, most likely as a consequence of the increased volume fraction of the ductile bcc phase. Attempts are made to rationalize the structural transformation.