Papers by Keyword: Intermediate Phase

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Authors: L. Levin, T. Werber, A. Katsman, Michael Atzmon, A. Ginzburg
Authors: Keizo Hashimoto, Kyoichi Seita
Abstract: The mechanical properties and the oxidation resistance of -TiAl at elevated temperatures have to be improved to be used in the severe environmental conditions. It has become clear that the addition of more than 4at.%Ta in TiAl demonstrates a superior oxidation to the other TiAl-X compounds, according to the weight gain results of cyclic oxidation experiments at 1173 and 1273K. Oxidation behaviors are strongly influenced by the Ta concentration in TiAl. XRD, SEM-EDS, and TEM-EDS observations have been carried out to determine the microstructures and the surface compositions of multi-layered oxide scales. It was revealed that a protective intermediate phase simultaneously formed between the substrate γ-TiAl and the oxide scale layer. The Ti53Al32Ta15 ternary compound exists as an equilibrium phase at 1373K, according to the published Ti-Al-Ta ternary phase diagram. This ternary compound can work as a barrier to some extent. It contributes to decelerating the diffusion of Ti and Al atoms and to decreasing the oxidation rate. The formation mechanism of the intermediate phase has been discussed in conjunction with diffusion in TiAl.
Authors: Andriy Gusak, A.O. Bogatyrev, A.O. Kovalchuk
Authors: Jie Dong, Z.F. Li, Xiao Qin Zeng, Wen Jiang Ding
Abstract: Intermediate phase growth in Mg-Al diffusion couples were studied with different intensity of a strong static magnetic field from 0 to 10 Tesla. Thickness measurement of the intermediate phases (Mg17Al12 and Al3Mg2) shows that with the increasing of magnetic field intensity, the growth rate of both intermediate phases is retarded. The decrease of the phase growth rate is ascribed to the suppressed Al, Mg atom interdiffusion in the diffusion couple under the static magnetic field. It is also found that the orientation relationship between couple interface and magnetic field direction has no influence on the growth of intermediate phases.
Authors: Shahram Ahmadi, Ali Shokuhfar, Arash Rezaei
Abstract: To respond the need of industries to the new materials with higher specific modulus and lower density than those of the older Al alloys, aluminum- lithium alloys have been invented and improved. Aging process is one of the most important methods to improve the mechanical properties of aluminum- lithium alloys which are in the heat treatable category of aluminum alloys. Low temperature and natural aging processes cause the "short range diffusion" of Cu atoms in the aluminum and the formation of the GP zones. In this research, stability of GP zones and the effects of these areas on physical and mechanical properties of AA2090 alloy were investigated by hardness, electrical resistance, DSC (differential scanning calorimetric) and tensile tests. Results show that endothermic effect in the DSC diagrams of AA2090 alloy at 180°C to 240°C can be related to the enthalpy of GP zones dissolution. Formation of GP zones in the structure increases hardness, tensile strength and electrical resistance of Al- Li C u (2090) alloys.
Authors: Šárka Msallamová, Kateřina Šálková, Michaela Fousová, Drahomír Dvorský, Jaroslav Jiřík, Tereza Šálková, Tomáš Hiltscher, Daniel Hlásek, Jan John, Martin Pták, Jiří Dohnal, Zdeněk Jáně
Abstract: The study deals with the material survey of a raw material, bronze axe and sickle from the Late Bronze Age. Artefacts were chosen from a set of about thirty objects, which were found in a ceramic pot near to Křenovice in the South Bohemia. The ancient technology of the axe and the sickle production was determined by the evaluating of structural properties using prepared metallographic sections. The chemical composition of a metal matrix and intermediate phases were determined using a scanning electron microscope with an EDS analyzer and X-ray fluorescence. The corrosion products of the artefacts were analyzed by X-ray diffraction. The results showed that the axe was made from partly wrought bronze (CuSn10) processed by subsequent recrystallization annealing. The bronze sickle (CuSn11) was a cast without any further mechanical processing or heat treatment. The material of the a raw material was found to be an arsenical copper alloy (CuAs1), which was probably used as a starting material for the bronze alloy production.
Authors: Yan Yi Liu, Wei Pan
Abstract: BaTiO3 powder was synthesized from BaCO3 and TiO2 using a domestic microwave oven. The samples were synthesized under different temperatures with various holding times. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to examine the phase compositions and morphologies of the result samples. The main phase obtained at 950°C was BaTiO3, and the intermediate phases Ba2TiO4 and Ba4TiO9 were also detected. The pure, well-crystallized BaTiO3 powder could be obtained at 1050°C within 10 minutes and the particle size ranged from 300~500nm. In comparison with conventional synthesis, faster speed and finer grains could be achieved through microwave heating.
Authors: A.S. Shirinyan, Andriy Gusak, P.J. Desré
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