Low Temperature Milling Research Articles

Study on milling flatness control method for TC4 titanium alloy thin-walled parts under ice fixation

Thin-walled parts are characterized by weak rigidity and are very prone to deformation during machining, which directly affects the machining accuracy and performance of the parts, so controlling the machining deformation of thin-walled parts is an urgent process problem to be solved. To address such problems, this paper proposes a flatness control machining method based on ice holding of workpieces. The method uses frozen suction cups to solidify liquid water to achieve stress-free clamping of workpieces. We conducted a low-temperature tensile test to investigate the low-temperature mechanical properties of the material. Comparative tests of ice-free and low-temperature ice-fixed milling were conducted to compare and analyze the changes of flatness and milling force in the two working conditions, to investigate the influence of machining parameters on the flatness of thin-walled parts, and to reveal the mechanism of low-temperature milling of ice-fixed workpieces. In addition, the low-temperature milling performance of titanium/aluminum alloy based on ice-fixation was compared. The results show that TC4 has good plasticity, high flexural strength ratio and strong resistance to deformation at low temperatures. Compared with no ice-holding, ice-holding machining effectively improves the flatness of the workpiece, and the order of the machining parameters affecting flatness is: feed rate > milling depth > spindle speed. The milling forces under ice-holding conditions were all greater than those without ice holding. The stiffness and hardness, resistance to damage and deformation of titanium alloy at low temperature are greater than those of aluminum alloy. This method provides a new method for high-precision machining of thin-walled parts.

Aero-Engine Blade Cryogenic Cooling Milling Deformation Simulation and Process Parameter Optimization.

For the machining of aero-engine blades, factors such as machining residual stress, milling force, and heat deformation can result in poor blade profile accuracy. To address this issue, simulations of blade milling were completed using DEFORM11.0 and ABAQUS2020 software to analyze blade deformation under heat-force fields. Process parameters such as spindle speed, feed per tooth, depth of cut, and jet temperature are used to design both a single-factor control and BBD test scheme to study the influence of jet temperature and multiple changes in process parameters on blade deformation. The multiple quadratic regression method was applied to establish a mathematical model correlating blade deformation with process parameters, and a preferred set of process parameters was obtained through the particle swarm algorithm. Results from the single-factor test indicated that blade deformation rates were reduced by more than 31.36% in low-temperature milling (-190 °C to -10 °C) compared with dry milling (10 °C to 20 °C). However, the margin of the blade profile exceeded the permissible range (±50 µm); therefore, the particle swarm optimization algorithm was used to optimize machining process parameters, resulting in a maximum deformation of 0.0396 mm when the blade temperature was -160 °C~-180 °C, meeting the allowable blade profile deformation error.

Microstructure and Magnetic Properties of Ce14Fe78Co2B6 Nanopowders Prepared by Ball Milling at Low Temperature

Ce14Fe78Co2B6 nanopowders with hard-magnetic properties have been successfully prepared by ball milling at low temperatures in liquid nitrogen. The morphology, structure, and magnetic properties of Ce14Fe78Co2B6 powders have been investigated using scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometry, respectively. It was found that powder ball milling at low temperature in liquid nitrogen, has the advantage that the oxidation of powders is inhibited and the particles rapidly reach nanometric dimensions. In comparison to the Ce14Fe78Co2B6 powders prepared by ball milling at room temperature, the powders milled at low temperature present a more uniform particle size and no rare-earth oxides, which leads thus to remarkable magnetic properties. The nanocrystalline Ce14Fe78Co2B6 powders with optimum characteristics, prepared at low temperature, have the size of 153 nm or less, present a coercivity of 5.1 kOe, and a saturation magnetization of 113 emu/g after milling for 6 h at low temperature. Low temperature milling may become a promising technique for the fabrication of high performance powders used for permanent magnets preparation.

Fabrication of remarkably magnetic-property-enhanced anisotropic Sm2Fe17Nx nanoflakes by surfactant assisted ball milling at low temperature

Anisotropic Sm2Fe17Nx nanoflakes with high performance were successfully prepared via surfactant-assisted ball milling (SABM) at low temperatures. Comparing with the conventional SABM at room temperature, these Sm2Fe17Nx nanoflakes possess more uniform particle sizes, much enhanced coercivity and remanence ratio (Mr/Ms), higher saturation magnetization and excellent magnetic alignment. Based on systematic investigations of phases, N content and magnetic properties as a function of milling time for nanoflakes fabricated at room and low temperatures, the effective inhabitation of the decomposition of Sm2Fe17Nx phase by low-temperature milling has been clearly evidenced. Our study indicates that the low-temperature milling may serve as a promising and new technique for fabricating the high-performance Sm-Fe-N anisotropic powders used in bonded magnets.

Tuning Ionic Clusters in Sulfide Glass-Ceramics for Superior Solid-State Electrolytes

The all-solid-state lithium batteries (ASSLBs) have drawn increasing interests and demands as the next-generation rechargeable batteries for electric vehicles and energy storage devices since they have much more potentials (e.g., higher safety, reliability, power density, and design flexibility) than conventional lithium batteries. However, all we know any further advances in ASSLBs are not possible without solving the current raising issues of ASSLBs, such as low lithium ion conductivity, structural instability, and high resistance of electrode/electrolyte interface. Especially, the unveiling the mechanism of lithium ion conduction in solid electrolytes, and the development of a superior solid-state lithium ion conductor are required. Here we present the recent advances and understandings in Li-P-S based solid electrolytes for the next-generation ASSLBs using a novel atomistic alloying and annealing process. Employing the low-temperature milling and quantitative bulk/surface analyses, we demonstrate the tuning ionic structures in sulfide glass-ceramics for superior solid-state electrolytes, and unveil the roles of atomistic alloying in the mechanochemical pulverization and high-temperature annealing in the amorphous-crystal transition to seek the highly active, stable, and versatile Li-P-S based solid electrolytes. Controlling ionic structures and understanding such atomistic alloying and annealing effects of lithium super-conducting sulfides provides insights for designing advanced solid electrolyte materials. We also believe these research activities lead to the promising technological advances and provide new guidelines in developing the sulfide based solid electrolyte for ASSLBs.

The structure and magnetic properties of Sm–Fe–N powders prepared by ball milling at low temperature

Sm–Fe–N powders have great potential to be used for preparing high-performance bonded permanent magnets because of their high anisotropy field and large saturation magnetization. In this work, we report the morphology, structure, oxygen content and magnetic properties of the Sm–Fe–N powders prepared by high energy ball milling at low temperature. Compared with the samples milled at room temperature, the Sm–Fe–N powders prepared at low temperature display more homogeneous morphology, less decomposition, lower oxygen content, and therefore enhanced magnetic performance. Our experimental results indicate that the low temperature milling will be a promising method for fabricating Sm–Fe–N bonded magnets with high-performance.

B13-P-07Evaluation of cross-sections of low melting point metals prepared by an FIB equipped with a cooling stage

A sample preparation technique, that is a front end of electron microscopy, has become highly important, and thus a choice of it affects a result of the evaluation. Sample preparation of low melting point metals is very difficult because they are soft and heat sensitive materials. The electron microscopic evaluation of them has been always discussed. In this study, a cooling stage was attached to an FIB-SEM for applying to the low melting point metals. Figure 1 shows comparison of cross-sections of lead solder prepared by ion milling at room temperature and low temperature [ 1 , 2 ]. By the room temperature milling, many cracks (arrows) are induced at grain boundaries. The low temperature milling gives a smooth surface without any cracks which produces a clear channeling contrast. Ion milling at a low temperature was confirmed to be very useful for sample preparation to achieve a high quality cross-section of low melting point metals.

Fabrication of novel cryomill for synthesis of high purity metallic nanoparticles.

The successful preparation of free standing metal nanoparticles with high purity in bulk quantity is the pre-requisite for any potential application. This is possible by using ball milling at cryogenic temperature. However, the most of ball mills available in the market do not allow preparing high purity metal nanoparticles by this route. In addition, it is not possible to carry out in situ measurements of process parameters as well as diagnostic of the process. In the present investigation, we present a detailed study on the fabrication of a cryomill, which is capable of avoiding contaminations in the product. It also provides in situ measurements and diagnostic of the low temperature milling process. Online monitoring of the milling temperature and observation of ball motion are the important aspects in the newly designed mill. The nanoparticles prepared using this fabricated mill have been found to be free standing and also free from contaminations.

Effect of milling temperature on nanoclusters and ultra fine grained microstructure of oxide dispersion strengthened steel

The effect of ball milling temperature on the mechanical alloying and subsequent microstructural evolution of ferritic oxide dispersion strengthened steel was studied. The mixtures of Fe–14Cr–3W–0.4Ti powder and Y2O3 were ball milled for 40 h at room-temperature, −70 °C, and −150 °C. As milling temperature decreased, the fraction of low angle grain boundaries increased. Final grain size after consolidation was greatly affected by the ball milling condition. The size of nanoclusters seems to be dependent on milling temperature too. Ultra-fine grain size with homogenous dispersion of Y–Ti–O nanoclusters was achieved by very low temperature milling.

Influence of Rice Sample Preparation and Milling Procedures on Milling Quality Appraisals

<abstract><title><italic>Abstract.</italic></title> <bold> </bold>The objective of this research was to investigate the effect of sample preparation and milling procedure on milling quality appraisals of rough rice. Samples of freshly harvested medium-grain rice (M202) with different initial moisture contents (MCs) ranging from 20.2% to 25.1% (w.b.) were used for this study. To create rough rice with varying quality, the samples were dried from their initial MC to a moisture content of 13.1% ±0.3% (w.b.) using air at different temperatures. Before milling, the MC of the samples was measured using three different methods: standard oven method, Dickey-John GAC 2100 (DKJ), and single-kernel moisture meter (SKM). The samples were milled using a McGill No. 3 mill. Three milling procedures were used: the standard western milling procedure, referred to as normal milling (NM), the southern milling procedure (SMP), and low-temperature milling (LM). The effect of storage after drying on quality appraisals was evaluated. Milling quality was compared based on total rice yield (TRY), head rice yield (HRY), whiteness index (WI), and lipid content (LC). HRY was found to be significantly affected by variation in initial MC, drying temperature, storage time after drying, and milling procedure. WI and LC were not significantly affected by these parameters. HRY decreased significantly with increased initial MC and drying temperature. The LM and SMP procedures significantly improved HRY up to 4.8% and 2.8%, respectively. HRY significantly increased with increase in storage time of dried rice up to four days, after which HRY was not affected by storage time. Regression models were successfully developed to predict HRY under tested rice conditions and milling procedures. The DKJ and SKM instruments, which are widely used in the rice industry, need to be calibrated at the full moisture range to ensure accurate results in MC measurement. The obtained results provide valuable information to achieve consistent, accurate, and reliable milling quality appraisals.

Temperature Effects in Al 5083 with a Bimodal Grain Size

ABSTRACTAn Al 5083 alloy with a bimodal grain size has been previously synthesized using a low-temperature milling process and consolidation via cold isostatic pressing (CIP). This material has been shown to exhibit greatly improved strength when compared to conventional aluminum alloys. Additionally, this material has shown sensitivity to test conditions. In this work, we studied the effects of temperature on the strain rate sensitivity of this material by examining its elastic and plastic properties though uniaxial tension tests conducted under a variety of conditions at temperatures up to 473 K. Serrated stress-strain curves were observed, indicating dynamic strain aging. Strain rate sensitivity was found to depend non-monotonically on the test temperature.

Three‐dimensional nanofabrication of polystyrene by focused ion beam

Focused ion beam micromachining provides a maskless and resistless technique for prototyping of structures from thermoplastic polymers, an example being the production of polystyrene microcantilevers with potential applications as micro/nanoelectromechanical systems sensors and actuators. The applicability of FIB technology is, however, often restricted by the damage created by high energy gallium ion bombardment and local beam heating, which can affect the desired properties and limit the minimum achievable size of the fabricated structure. To investigate the ion-induced damage and determine the limitations of the technique for polymer nanofabrication, we have exposed thin polystyrene film to the ion beam at varying ion doses, ion energies and specimen temperatures. Ion doses ranging from 10(16) to 10(18) ions cm(-2) show significant gallium implantation, redeposition of sputtered material and chemical degradation in the polymer. Raman results show that the local heating in polymer during milling is severe at room temperature, damaging the aromatic carbon bonding (C = C) in particular. These observations are supported by the results of a beam heating model and Monte Carlo simulations. The chemical degradation caused by local beam heating is found to be significantly reduced by cooling the specimen to -25°C during milling. This is consistent with observations that reversible and repeatable thermal actuation of a fabricated polystyrene-platinum microcantilever is only observed when the cantilever is prepared at low temperature milling. Using this cooling approach, polymer structures can be fabricated with dimensions as low as 200 nm and still retain a sufficient volume of material unaffected by the ion beam.

Effect of boldo (Peumus boldus M.) pretreatment on kinetics of supercritical CO2 extraction of essential oil

This work examined the effect of the solid matrix on supercritical carbon dioxide (SC CO2) extraction of essentials oils from boldo leaves (Peumus boldus M.) subjected to rapid decompression of a CO2-impregnated sample, conventional milling, and low-temperature milling. Low-temperature conditioning prior to milling decreased heat-driven losses of volatile compounds during milling, as attested by a higher extract yield for low-temperature (10.8g extract/kg extract-free substrate) than conventionally (9.63g/kg) milled sample. Extract yield was even larger for the rapidly decompressed sample (11.4g/kg). Results of SC CO2 extraction experiments carried out at 40°C and 10MPa were adjusted to a diffusional model using the effective diffusivity of the extract in the solid matrix (De) and a single partition of essential oils between solid substrate and SC CO2 as best-fitting parameters. A microstructural factor (FM), which was estimated as the ratio between the binary diffusion coefficient of the essential oil in SC-CO2 under extraction conditions and De, was used to characterize the effect of sample pretreatment on extraction rates. Values of FM for rapidly decompressed (202) and low-temperature milled (1740) samples were smaller than value for conventionally milled samples (2200), which revealed that the two first treatments disrupted secretory cavities in boldo leaves more effectively than the third. This was confirmed by light microscopy observations. The work included also measurements using oregano bracts (Origanum vulgare L.) as the substrate to confirm literature reports on the SC CO2 extraction of pretreated bracts and to serve as a reference to our main results with boldo leaves. Trends with oregano coincided with those of boldo.

Preparation of ultrafine CsCl crystallites by combined cryogenic and room temperature ball milling

The present investigation reports the preparation and microstructural characterization of ultrafine CsCl crystallites using combined cryogenic and room temperature (RT) mechanical milling. The milling has been performed in evacuated WC vials under high purity argon atmosphere. The low temperature milling has been utilized as an effective means of rapid fracturing of the CsCl crystallites. This was followed by RT milling for different time durations. The final crystallite size obtained is 10 ± 6 nm for sample cryo-milled for 11 h and subsequently RT milled for 35 h. The experimental findings indicate the strong effect of duration of cryo-milling on the final size of the crystallites. The prolonged room temperature milling leads to increase of the crystallite size due to deformation-induced sintering. The results have been discussed in the light of currently available literature.

Low temperature milling of the LiNH2 + LiH hydrogen storage system

Ball milling of the LiNH2 + LiH storage system was performed at 20°C, -40°C, and -196°C, and the resulting powders were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), specific surface area (SSA) analysis, and kinetics cycling measurements. Ball milling at -40°C showed no appreciable deviations from the 20°C sample, but the -196°C powder exhibited a significant increase in the hydrogen desorption kinetics. NMR analysis indicates that a possible explanation for the kinetics increase is the retention of internal defects generated during the milling process that are annealed at the collision site at higher milling temperatures.

Effect of deproteination on bone mineral morphology: implications for biomaterials and aging

Bone mineral morphology is altered by processing and this is rarely considered when preparing bone as a bioimplant material. To examine the degree of transformation, a commercial, coarsely particulate bone mineral biomaterial produced by prolonged deproteination, defatting, dehydration, and heating (donor material) was compared with similar particles of human bone (recipient material) prepared optimally by low-temperature milling. The two powders were freeze-substituted and embedded without thawing in Lowicryl K4M before sectioning for transmission electron microscopy (TEM) (other aliquots were processed by traditional TEM methods). To maximize resolution, electron micrographs were image-enhanced by digitization and printed as negatives using a Polaroid Sprint Scan 45. In addition to their morphology, the particles were examined for antigenicity ( specific by reference to fluorescein isothiocyanate [FITC]-conjugated fibronectin, and nonspecific by reference to general FITC-conjugated immunoglobulins). Results showed that the optimally prepared human bone fragments stained discretely for fibronectin with negligible background autofluorescence. In contrast, the bioimplant fragments stained extensively with this and any other FITC-conjugated antibody and, unlike fresh bone, it also autofluoresced a uniform yellow. This difference was also expressed structurally and, although the bioimplant mineral consisted of rhomboidal plates up to 200 nm across and 10 nm thick, the optimally prepared bone mineral was composed of numerous clusters of 5-nm-wide sinuous calcified filaments of variable density and indeterminate length (which became straight needles 50 nm long and 5 nm thick following traditional chemical TEM fixation/staining). It was concluded that the inorganic phase of bone is both morphologically and immunologically transmutable and that, in biomaterials, the transformation is apparently so great that a broad indigenous antigenicity is unmasked, increasing the likelihood of resorption or rejection. This marked change may also provide preliminary insight into a more modest natural aging phenomenon with the localized lateral fusion of calcified filaments into less flexible, more immunologically reactive fenestrated plates.

Forced mixing and nanoscale decomposition in ball-milled Cu–Ag characterized by APFIM

Ag 50Cu 50 alloys are prepared by high energy ball milling at different controlled temperatures, 85 K, 315 K and 453 K, with milling times long enough to reach steady-state. Atom probe field ion microscopy (APFIM) is used to characterize the atomic mixing forced by low temperature milling and to study the nanocomposite materials stabilized by elevated temperature milling. A new method is devised that makes it possible to prepare sharp tips from ball-milled powders. Statistical analysis of the APFIM composition profiles is used to determine the degree of mixing as a function of the length scale. These results are compared with the ones obtained from kinetic Monte Carlo simulations. Cryo-milling results in nearly random mixing of copper and silver, whereas the mixing achieved by milling at 315 K is calculated to be around 70%. 453 K milling results in the decomposition into copper-rich and silver-rich regions at a scale of ≈25 nm.

A Pilot Scale Study for Banana Starch Production

AbstractBanana starch production was studied in pilot plant scale. Immersion the green banana in hot water at 70°C for 5 to 6 min could facilitate the peeling process. Low temperature milling decreased viscosity of the resulting starch suspension. Addition of 0.5‐N NaOH solution during milling, and left the milled banana paste overnight before screening could improve the efficiency of starch extraction. Remilling the pomace of 1st screening step could increase yield. The studied process procedure resulted a yield for banana starch of 70%. The purity of the product was approximately 94%.

Infrared spectroscopic studies on polyethylene, 5. The measurement of chain branching on powder polyethylene specimens

AbstractThe scope and limitations of the potassium bromide disc technique for the infra‐red determination of chain branching in small samples of polyethylene in powder form have been assessed. Many of the samples encountered have an average particle size, prior to grinding with potassium bromide, of about 100 μm and very satisfactory results have been obtained, but the presence of larger particles leads to poor quality discs and inferior results. The well established double beam technique proves suitable for removing the interfering methylene absorption and compensation with polymethylene in the form of a film rather than as a pressed disc is preferable. Difficulties were encountered in preparing branching standards in a uniform and fine powder form, to avoid variation of the absorption coefficient of the 1 378 cm−1 methyl band with particle size. Such powders are best obtained by precipitation from solution rather than by low temperature milling. Despite these problems chain branching measurements may be made with a precision of between 5 and 10% and an accuracy of about 15%.