Papers by Keyword: Isothermal Annealing

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Authors: Ahmed G. Attallah, M.A. Abdel-Rahman, M. El-Sayed, A.A. Ibhraim, S.A. Aly, Emad A. Badawi
Abstract: The electrical resistivity and the corresponding mechanical properties (hardness) of some 5xxx Al-Mg alloy processed by plastic deformation were investigated. Plastic deformation was performed at room temperature. Isothermal annealing produced a significant change in both the electrical and mechanical properties of the samples. As the annealing time was increased, the resistivity and hardness up to full recovery. The activation enthalpy of migration of defects was determined, was found to be 0.234±0.06 eV, 0.218±0.049 eV, 0.316±0.016 eV 0.232±0.012 eV for 5005, 5251, 5052 and 5754 alloys, respectively.
Authors: M.A. Abdel-Rahman, M.S. Abdallah, N.A. Kamel, Emad A. Badawi
Abstract: Recovery behavior of 20% plastically deformation of casting AlSi11.35Mg0.23 in various stages of isochronal annealing has been investigated by positron Lifetime (LT). The experimental results show that the positron mean lifetime is a function of annealing temperature. Lifetime of the positron annihilating in perfect lattice is 187.3ps and in 20% deformed is 229.8 ps. There are two regions in the isochronal annealing, one of them relating to the point defect and the other to the dislocation. The activation enthalpy for the dislocation is calculated from the isothermal study in the dislocation region from (575-675) K by slow and fast cooling as 0.16±0.02 and 0.53±0.06 eV respectively.
Authors: Z.W. Hsiao, C.C. Fu, P.H. Tsai, Jason S.C. Jang, S.R. Jian, J.C. Huang
Abstract: The (Zr53Cu30Ni9Al8)99.5Si0.5 bulk metallic glass (BMG) rods, 3 mm in diameter, with different crystallization fraction for compression test were prepared by isothermal annealing the as-cast BMG rods at the temperature in the middle of supercooled temperature region for different time period in vacuum, respectively. The result of compression test revealed that the fracture strength of these samples increases with the crystallization ratio at the beginning, then decreases rapidly at 40 vol.% crystallization fraction. In addition, the best mechanical performance with 1970MPa yield strength and 3 % plastic strain occurs at the sample with 30 vol.% nanocrystalline phase (with an average size about 50 nm). This was suggested these homogeneous distributed nanocrystals which embedded in the matrix may act as obstacles to branch the primary shear band into multiple shear band and result in improving the ductility.
Authors: Jung Il Lee, Jong Bum Park, Sin Wook You, Joo Ho Lee, Il Ho Kim, Kyung Wook Jang, Soon Chul Ur
Abstract: Clathrate Ba8Al16Si30 was produced by arc melting and annealing effects on the microstructure and thermoelectric properties were investigated. The phase transformation behavior of arc-melted Ba8Al16Si30 was examined by thermogravimetric analysis, differential scanning calorimetry, hardness test, X-ray diffraction and scanning electron microscope analyses. Isothermal annealing was carried out to induce the transformation to a thermoelectric phase at 500°C to 700°C for 5 hrs. Thermoelectric properties in the temperature range between 300K and 600K were measured and evaluated. Electrical conductivity was decreased and Seebeck coefficient was increased with increasing isothermal annealing temperature. The arc-melted and the isothermal annealed specimens represented n-type conduction at temperatures examined, and they showed reliable thermoelectric behaviors.
Authors: Eugene P. Yelsukov, V.M. Fomin, O.M. Nemtsova, D.A. Shklyaev
Authors: Peng Fei Liu, Wen Jun Chen, Jun Jun Li, Ru Long Zhou, Bo Zhang
Abstract: In this work, we have developed a series of amorphous alloy ribbons of Fe75Co4B13Y4Nb4-xNix(x=0, 0.5, 1, 2, 3 and 4) which were prepared by industrial purity alloy. Besides, the effects of Ni substitution and isothermal annealing on the saturation magnetization (Ms) and intrinsic coercive force (jHc) were systematically investigated. The SQUID-VSM data pointed out the Ms has been increased by Ni content addition with largest enhanced by 57 % from 114 emu/g to 180 emu/g. After quickly annealing at the optimal temperature, the Ms reached 199 emu/g and jHc decreased from 50 Oe to 33 Oe. DSC measurements displayed that this system has a multi-step crystallization in the heating process. Under the premise of maintaining the excellent amorphous forming ability (AFA), the gap between the two crystallization peaks was broadened with Ni addition, which is good to the forming of α-Fe phase at the annealing treatment. And this was also consistent with the X-ray diffractometer (XRD) results. The Scherrer formula calculated results suggested that isothermal annealing has significant effect on size of α-Fe nanocrystals in annealing process, which obvious affect the Ms and jHc. The annealing temperature and time can not only affect the precipitation of nano-crystalline, but also control the grain size. Hence, an appropriate annealing process is very important to improve the properties of these iron-based nanocrystalline magnetic materials. In conclusion, the results will help us to understand the influence of Ni elements and isothermal annealing on the microstructure and magnetic of Fe75Co4B13Y4Nb4-xNix amorphous alloys.
Authors: M.A. Abdel-Rahman, N.A. Kamel, Abdullah A. Refeay, Yahia A. Lotfy, Emad A. Badawi
Abstract: Positron annihilation lifetime (PAL) is one of the most important nuclear techniques used in material science. Electrical measurements are also used in material science. Samples of 25 % deformation have been used for these studies. Both positron annihilation lifetime and electrical measurements were used to determined the activation energy of migration the dislocation in 7075 alloy. The isothermal annealing measurements were performed at 643, 663, 683 and 703 K. The activation energy of migration the dislocation are obtained as 1.35 ± 0.16 eV and 1.25 ± 0.05 eV for positron annihilation lifetime and electrical techniques respectively.
Authors: J. Sitek, M. Miglierini, I. Tóth, Jozef Lipka
Authors: Carlos Capdevila, Tommy De Cock, Francisca García Caballero, Carlos García de Andrés
Abstract: In this work the prominent influence of Particle Stimulated Nucleation (PSN) on the overall process of nucleation and subsequent grain growth is discussed and a global recrystallisation kinetics model is proposed. This model accounts for the effect of the most relevant industrial parameters, such as cold reduction and annealing temperature. Moreover, not only the role of the cementite content, which is function of the nominal carbon content, is included in the model, but also the morphology of the second phase particles. Experimental evidence is given to ascertain the accuracy of the theoretical predictions.
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