Phase transformations in mechanically alloyed Al-Cu-Cr powders

Mechanical alloying was used to form a decagonal phase in the Al-Cu-Cr system. Elemental powders of Al67Cu20Cr13, Al75Cu10Cr15, Al65Cu24Cr11, Al69Cu21Cr10 and Al78Cu10Cr12 compositions (in at. %) were mechanically alloyed in a planetary ball mill. Annealing in the temperature range of 500 to 550 0C results in the formation of binary and ternary compounds including the decagonal quasicrystalline phase that was found to be stable at least up to 800 0C and was present in various amounts in all investigated alloys. No icosahedral quasicrystalline phase was found in the samples. The maximum content (95 vol. %) of decagonal quasicrystalline phase was observed for Al69Cu21Cr10 compound annealed at 635 0С. Further increase in the annealing temperature results in the quasicrystalline phase transformation into ψ-Al65Cu25Cr10 phase, which is an approximant phase to icosahedral quasicrystal

Structure and magnetic properties of mechanically alloyed Fe3-xAlCrx powders

Mixtures of elemental powders of Fe3-xAlCrx composition, where x ∈ (0.8 -1.2) were mechanically alloyed in the AGO-2U planetary ball mill. Obtained powders consist of particles with median size of 0.5-1.6 µm; increase in the Cr content results in the decrease in the size of particles. According to the X-ray data, all of the as-milled alloys possess a single-phase disordered b.c.c. structure. Increase in Cr content results in the decrease in the grain size of alloys, whereas the dependence of the lattice parameter on the chemical composition is not conclusive. Mössbauer spectra for most of the alloys shows that iron atoms in this alloys, in spite of the fact that only one phase was detected using the X-ray diffraction, exist both in ferromagnetic and non-ferromagnetic conditions

Ball milling effect on the properties of ultra high molecular weight Polyethylene - bronze composite

Peculiarities of the technology to produce a composite material based on ultra-high molecular weight polyethylene (UHMWPE), mechanically activated with bronze powder are considered along with the properties of the produced material. Samples of the press-composition on the basis of UHMWPE with 0 up to 97.5% of the bronze powder addition were prepared by joint mechanoactivation of super-high-molecular polymer and the bronze powder using planetary mechanoactivator MPF-1 and toroidal vibration mechanoactivator MV-0.05. Packed density of the press-composition was analyzed as a function of the formula and the mechanoactivation technique used. Bulk samples for the tests were obtained by direct pressing. The properties of the samples were studied, and the relations between the density of the material, the physical and mechanical and thermal-physical properties and the concentration of the bronze powder in the material and the milling time were investigated

Structure and propertties of ball milled utrahigh-molecular weight Polyethylene - clay composite

In this work the composite material based on polymer matrix filled with clay is studied. The preparation of powder composition consists of mechanical activation of substances and further common ball milling of polymer and clay in a high energy planetary ball mill. The process is divided into two stages; the first stage involves crushing of clay to obtain a nanosized powder, and in the second stage preparation of powdered nanocomposite is carried out. New clay-polymer composite shows considerable increase in modulus of elasticity and a decrease in coefficient of friction

ИССЛЕДОВАНИЕ ФАЗОВОГО И ПРИМЕСНОГО СОСТАВА ЛЕНТ КАТОДНЫХ СПЛАВОВ Pd—Ba и Pt—Ba

We have  studied the  phase and  impurity composition of Pd—Ba  and  Pt—Ba cathode alloys obtained on an A 535.02TO arc melting plant using a technology developed by AO Shokin NPP Istok. The study  showed that  the  concentration of detrimental impurities (C; Zn; Cu; Al) in the specimens is within the allowed range. Pd—Ba tapes are rich in Ba but this does not compromise their quality. We have confirmed the earlier found domination of two−phase composition in Pd—Ba and Pt—Ba alloys where  one of the phase is an intermetallic compound (Pd5Ba, Pt5Ba) and the other  is a noble metal(the matrix). The intermetallide is distributed in the  platinum  metal  matrix quite inhomogeneously, this tangibly impairing the operation parameters of cathodes produced from these alloys. For the first time we have shown the high efficiency  of transmission electron microscopy for studying Pd—Ba and  Pt—Ba cathode alloys. We have  for the first time found the Pd2О phase in Pd—Ba. It may significantly reduce the secondary electron emission coefficient and the quality of devices based on this alloy. We have determined the Pd and Pd5Ba grain size in the Pd—Ba alloys and the Pt and Pt5Ba grain size in the Pt—Ba alloys. All the Pd and Pt5Ba grains contain high densities of randomly arranged dislocations, and Pt5Ba grains  contain internal  stresses. Recommendations have been given concerning the improvement of the current Pd—Ba and Pt—Ba cathode alloy tape  technology.Изучен примесный и фазовый состав лент катодных сплавов Pd—Ba и Pt— Ba, полученных на установке дуговой плавки А 535.02ТО  по технологии, разработанной в АО «НПП «Исток им.  Шокина». Установлено, что концентрация вредных примесей (C, Zn, Cu, Al) в исследованных образцах не превышает допустимой нормы. Ленты состава Pd—Ba содержат повышенную концентрацию Ba, однако  это не сказывается на их качестве.Подтверждена обнаруженная ранее превалирующая двухфазность сплавов Pd—Ba и Pt—Ba: одна из фаз — интерметаллическое соединение (Pd5Ba, Pt5Ba),  вторая — благородный металл (матрица). При этом интерметаллид очень неравномерно распределен в матрице металла платиновой группы, что существенно понижает эксплуатационные  характеристики катодов на основе этих сплавов. Впервые показана высокая эффективность просвечивающей электронной микроскопии для исследования катодных сплавов Pd—Ba и Pt—Ba.В сплаве Pd—Ba впервые обнаружена фаза Pd2О. Это может приводить к существенному понижению коэффициента вторичной электронной эмиссии и падению эксплуатационных характеристик приборов на базе этого сплава. Определен размер зерен Pd и Pd5Ba в сплавах Pd—Ba, и зерен Pt и Pt5Ba в сплавах Pt—Ba. Обнаружено, что во всех зернах Pd и Pt5Ba наблюдается высокая плотность хаотически расположенных дислокаций, внутри зерен Pt5Ba имеются напряжения.Приведены рекомендации по совершенствованию существующей технологии получения лент катодных сплавов Pd—Ba и Pt—Ba

Mechanical Properties and Chemical Resistance of New Composites for Oil Pump Impellers

In this paper, a new class of high-performance composites and a method of their production based on the carbonization of an elastomeric matrix are proposed. The use of elastomeric matrix makes it possible to manufacture products with complex shapes, while the subsequent carbonization can significantly improve their properties by changing the chemical nature of the elastomeric matrix. Such an approach can reduce the products’ machining cost, especially for composites reinforced with super hard fillers such as silicon carbide at high filling degrees. Low-temperature carbonization makes it possible to obtain composites with mechanical behavior similar to that of ceramics. In contrast to classical elastomeric materials, the nitrile butadiene rubber (NBR)-based compounds were highly filled (300 parts per hundred rubber-PHR) with different carbon fillers and silicon carbide; then cured and carbonized at low-temperature 360 °C with the carbonization cycle of 12 h. The feasibility of the production method was validated through the manufacturing of products with complex shapes—impellers for electric centrifugal pumps. It was found that the carbonized composites have good chemical resistance and low water absorption. The composites have high Shore D hardnesses (93–96), ultimate tensile strengths (62–85 MPa), Young’s moduli (17–24 GPa), and compressive strengths (155–181 MPa)

Artificial muscles based on coiled UHMWPE fibers with shape memory effect

Ultra-high molecular weight polyethylene (UHMWPE) fibers drawn at drawing ratio of 6 (pre-deformation strain 500%) demonstrating the obtained one-way shape memory effect. Artificial muscles have been manufactured in the form of coiled UHMWPE fibers. Isometric recovery stress and recovery strain of the fibers were measured during heating by using a dynamic mechanical analyzer (DMA). As a result, the fibers were capable to demonstrate large contraction of 78% (recovery strain of 93%) due to the entropic elasticity. The recovery stresses of the fibers reach up to 27 MPa. The work of stroke cycle for coiled artificial muscles with a constant stress of 1 MPa was recorded. Artificial muscles based on coiled UHMWPE fibers have a large stroke of 64 %. The structural mechanisms of muscle-like behavior were discussed

Quasicrystalline phase formation by heating a mechanically alloyed Al65Cu23Fe12 powder mixture

Elemental powder mixtures of Al65Cu23Fe12 composition milled for two and four hours in a planetary ball mill were used to form quasicrystals. Annealing of the as-milled samples led to complex solid-state transformations. During the heat-up a sequence of solid-state reactions takes place in the as-milled powder. These reactions were studied both by differential scanning calorimetry and X-ray diffraction methods. An analysis of the phase formation shows the effect of the difference in the thermodynamic driving forces, such as the positive heats of mixing for the Cu-Fe system and the negative ones for the Al-Fe and Al-Cu systems, on the phase transformation consequence