Papers by Keyword: High Energy Milling (HEM)

Abstract: This paper applied to relations of the milling time、flakes thickness and diameter size D50 of Al-flakes by High Energy Milling(HEM) use the Benjaminm collision model. Through established of the collision model, the relationship of various technical indicators can be calculated of the flakes, and it can be used to guidance of the preparation and optimize the process.

Abstract: The aim of this work is to obtain and characterize the Niobium Carbide (NbC) by a suitable high energy milling technique using a SPEX Mill vibratory type and niobium and carbon (graphite) powders. Since this carbide is scarced in the national market and it’s necessary to apply this NbC as a reinforcement in two molybdenum high speed steels (AISI M2 and AISI M3:2) object of another work motivated this research. The powders were submitted to a high energy milling procedure for suitable times and conditions and then were characterized by means of Scanning Electronic Microscopy (SEM) and X-ray diffraction (DRX) techniques. The ball-to-powder weight ratio was 10:1. The analyzed samples showed that the high-energy milling is an alternative route of the NbC synthesis.

Abstract: This work was observed the phase formations of the mixture Al-Cu-Fe processed vial mechanical alloying, powders pressing at room temperature and subsequent heat treatment. The mixture of powders was made on the nominal composition Al65Cu20Fe15. A mill of high energy of the horizontal atrittor type was used to process the powders mixtures, in fixed time of two hours of milling. After milling, the powders were pressing in a die closed, with a diameter of about 28mm. The samples were observed by optical microscopy and analyzed X-ray diffractometry. The results obtained in this study provide a basis for setting parameters may be used as a basis for future research and possible applications.

Abstract: This work reports an investigation about the influence of the environment of milling on the characteristics of the powders and on the structure and density of sintered samples made of these powders. Mixtures of composition W-30wt%Cu were milled for 51 hours in a high energy planetary mill in dry and wet (cyclohexane) conditions. The milled powders have composite particles. The powders were pressed and sintered at 1050º, 1150º and 1200°C under flowing hydrogen. The isothermal times were 0 minutes for the first two temperatures and 60 minutes for the latter. The samples reached around 95% of relative density. The powders were characterized by means of XRD and SEM. The sintered samples were characterized by means of SEM, optical microscopy and density measurement.

Abstract: Highly pure Ti3AlC2 powder was fabricated by combination of high energy milling and heat treatment with Ti, C and Al as starting materials. The details of reactions and phase evolution in fabrication process were investigated. The results shown that the Ti-Al intermetallics, Ti3AlC2 and TiC were formed in high energy milling. The as-milled powders were heat treated subsequently, and the Ti3AlC2 powder with high purity was produced from the reaction among Ti-Al intermetallics, Ti3AlC2 and TiC at relative low temperature (1100 °C).

Abstract: Al2O3/Ti2AlC composites were synthesized by high energy milling and hot-pressing at 1200°C in a vacuum furnace with a pressure of 4.8×10-2 Pa, using Ti, Al and C powder as raw materials. The effect of sintering temperature on the reactions, phase composition and microstructure of the synthesized products were investigated. The results show that the TiC and TiAl intermetallics composite powders were synthesized during the milling process. After the hot pressing, Ti2AlC phase was formed by the reaction between TiC and TiAl. A small amount of Al2O3 was also produced because of the oxidation of Al in the hot press process, which formed Al2O3/Ti2AlC composite together with the Ti2AlC at 1200°C. The fine grained Al2O3 particles disperse within Ti2AlC uniformly, which play a important role to strengthen Ti2AlC matrix, resulting in the increase of flexural strength and fracture toughness from 250 to 275.4MPa, 9.8 to 10.5MPa•m1/2, respectively.

Abstract: Ti2AlC/Al2O3 nanocomposites were synthesized by high energy milling with Ti, C, Al and TiO2 as initial materials. The formation and evolution of phases in high energy milling and following heat treatment were investigated by X-ray diffractometer (XRD). The results show that the raw materials of Ti, C, Al and TiO2 were pulverized to ultrafine particles, and some of them transformed to amorphous phase. When the as-milled powders were heat treated in vacuum atmosphere, TiC was firstly produced and released large amount of reactive heat, which resulted in the reaction between Ti and Al to produce intermediate phases of the TixAly (TiAl3, TiAl, and Ti3Al) intermetallics. The reaction between Al and TiO2 produced Al2O3 phase. The TixAly intermetallics and the residual Ti and Al transformed to TiAl equilibrium phase. Finally, the TiAl intermetallics and the TiC reacted to yield Ti2AlC, which produced Ti2AlC/Al2O3 nanocomposite together with the former in-situ formed Al2O3.

Abstract: Ti2AlC powders with high purity were successfully synthesized via high energy milling and heat treatment of Ti, C and Al powders. The effects of composition and thermal treatment on the formation and purity of Ti2AlC were examined in detail. The results shown a mechanically induced self-propagating reaction (MSR) was triggered to form Ti3AlC2, TiC and TiAlx during the high energy milling. When the as-milled powders were heat treated, Ti2AlC was initially formed by the reaction between TiAl and TiC. With continuously increasing temperature, Ti2AlC was also produced by the reaction between TiAl and Ti3AlC2.

Abstract: The ternary layered machinable Ti3SiC2 ceramics were synthesized at 1300°C by high-energy milling and hot pressing sintering using Ti,Si and C powder as starting material. The reaction mechanism was examined by XRD, SEM and thermodynamic analysis. The results show that Ti-Si-C powders were transformed to Ti, Si and little TiSi, SiC,Ti5Si3 intermetallics by milled for 18 hours. In this process, the little Ti and C transformed to TiSi phase in early stage, and then the most of residual elements reacted to form SiC and Ti5Si3 intermetallics. Finally, Ti, Si, SiC, Ti5Si3 intermetallics and TiSi reacted to yield Ti3SiC2 by hot pressing sintering. And the sintering temperatures had a significant impact on the yielded content of Ti3SiC2 phase. Besides. The Ti3SiC2 would decompose if the temperature was high enough.

Abstract: High voltage zinc varistors was synthesized by high energy milling with Pr6O11 doped ZnO-Bi2O3 system as raw materials. The effects of milling time and sintering temperature on the electrical properties were investigated. The results show that high-energy milling decreases the sintering temperature of the ZnO varistors. The material derived from high-energy milling exhibit high density and good electrical properties at the sintering temperature from 1080 to 1180°C. The samples sintered at 1100 °C have average crystalline grain size of about 5 µm with the optimum values of electrical properties, gradient voltage V1mA is 371 V/mm, leakage current IL is 0.62 µA, non linear coefficient α is 60.