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Comparing short–range and medium–range ordering in Cu–Zr and Ni–Zr metallic glasses – Correlation between structure and glass form ability
, Article Journal of Non-Crystalline Solids ; Volume 499 , 2018 , Pages 227-236 ; 00223093 (ISSN) ; Tavakoli, R ; Foroughi, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
According to recent studies, Cu–Zr and Ni–Zr binary alloying systems are very similar based on known glass-forming ability criteria, however, they exhibit significant difference in glass-forming ability in practice. In this work, local atomic structures of Cu–Zr and Ni–Zr metallic glasses are studied by molecular dynamics simulation to explain the source of mentioned difference. The total and partial distribution functions, coordination number and voronoi analysis are utilized to characterize the local atomic structures around Zr, Ni and Cu atoms. It was found that the local environment around Zr atoms is almost similar in both systems. The difference in the atomic structure in these systems...
Artificial neural network modeling for evaluating of epitaxial growth of Ti6Al4V weldment
, Article Materials Science and Engineering A ; Volume 432, Issue 1-2 , 2006 , Pages 184-190 ; 09215093 (ISSN) ; Ebnonnasir, A ; Foroughi, A ; Sharif University of Technology
2006
Abstract
The effect of epitaxial growth on microstructure of Ti-6Al-4V alloy weldment was examined by artificial neural networks (ANNs). The microplasma arc welding (MPAW) procedure was performed at different currents, welding speeds and flow rates of shielding and plasma gas. Microstructural characterizations were studied by optical and scanning electron microscopy (SEM). Finally, an artificial neural network was developed to predict grain size of fusion zone (FZ) at different currents and welding speeds. The results showed that a coarse primary β phase develops in the fusion zone as a result of epitaxial nucleation on coarsened β grains near the heat affected zone (NHAZ) which grow competitively...
Viscosity estimation of semi-solid alloys by drop weight backward extrusion test under high speed deformation
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 379-384 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Khosravani, A ; Foroughi, A ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
A simple method for estimating the apparent viscosity of semi-solid alloys was investigated. A drop weight of 50Kg and backward extrusion equipments were used to test the deformation. Backward extrusion was employed in a closed die system due to the very little separation of liquid from solid phases compared with other methods at very high deformation rate. The half of the calculated impact velocity, 700mm/s was considered as an average velocity for deformation during the test, since the slop of the velocity changes against time is constant in the middle stage of the deformation. The initial height of the sample and the thickness of the residual compressed solid at the bottom of the cup were...
Morphological features of silicon rich phase in powder thixoformed spray atomized hyper-eutectic Al-Si alloy
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 493-498 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Nategh, S ; Foroughi, A ; Narimannezhad, A ; Khosravani, A ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
Microstructural evolution of the spray atomized and powder thixoformed hyper-eutectic A390 aluminum alloy was investigated. The spray atomized powder revealed homogeneous and very fine silicon particles distribution, due to the rapid solidification of the alloy. The semi-solid powders were extruded into a closed die cavity through a hole for the plastic deformation of the powder particles. A drop forge of 45kg weight at different heights was used in this investigation. Remarkable rearrangement and growth of the silicon rich phase was revealed in the final stage
Microstructural evolution of AZ91 alloy containing 3%Ca prepared by cooling slope
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 427-432 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Davami, P ; Narimannezhad, A ; Foroughi, A ; Kiani, M ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
Globulization of the grain refined AZ91 magnesium alloy with Ca on a cooling slope was investigated. Dendritic morphology of the grains was transferred into round and well distributed small particles as a result of grain-refinement effect of Ca in the alloy. Semi-solid holding of the alloy was carried out at different temperatures to improve the spherecity of the globules. Results show that, remelting at 540 °C for 30 min provides the best shape factor for the alloy. The study of coarsening kinetic in this alloy showed lower growth rate alternative other research which used same condition for produce semi-solid billet just in using Ca
Semisolid joining of zinc AG40A alloy by partial remelting and mechanical stirring
, Article Semi-Solid Processing of Alloys and Composites 10 - Selected, peer reviewed papers from the 10th International Conference on Semi-Solid Processing of Alloy and Composites, S2P 2008, Aachen, 16 September 2008 through 18 September 2008 ; Volume 141-143 , 2008 , Pages 225-230 ; 10120394 (ISSN); 9771012039401 (ISBN) ; Aashuri, H ; Kokabi, A. H ; Khosravani, A ; Kiani, M ; Foroughi, A ; Sharif University of Technology
Trans Tech Publications Ltd
2008
Abstract
A technique to achieve the globular weld structure using stirring the localized semisolid zone during butt-joining of zinc AG40A (Zamak-3) die cast alloy is reported. Since the semisolid temperature range of this alloy is very narrow, the accurate controlling of weld pool temperature must be considered. By presented process, globular microstructure of the weld zone can be achieved. Moreover the near weld zone would have the globular structure due to semisolid holding. A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately. A heating element was embedded in a castable ceramic block while a stream of gas could pass closely around the hot element length....