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Showing 4 results for M. Shahmiri

M. Ghalambaz,, M. Shahmiri, Y. H. K Kharazi,
Volume 4, Issue 1 (winter & spring 2007 2007)

Abstract: Problems such as the difficulty of the selection of processing parameters and the large quantity of experimental work exist in the morphological evolutions of Semisolid Metal (SSM) processing. In order to deal with these existing problems, and to identify the effect of the processing parameters, (i.e. shearing rate-time-temperature) combinations on particle size and shape factor, based on experimental investigation, the Artificial Neural Network (ANN) was applied to predict particle size and shape factor SSM processed Aluminum A.356.0 alloy. The results clearly demonstrated that, the ANN with 2 hidden layers and topology (4, 2) can predict the shape factor and the particle size with high accuracy of 94%.The sensivity analysis also revealed that shear rate and solid fraction had the largest effect on shape factor and particle size, respectively. The shear rate had a reverse effect on particle size.
M. Ghalambaz, M. Shahmiri,
Volume 5, Issue 3 (Summer 2008 2008)

Abstract: Cooling slope-casting processing is a relatively new technique to produce semisolid cast feedstock for the thixoforming process. Simple equipment, ease of operation, and low processing costs are the main advantages of this process in comparison with existing processes such as mechanical stirring, electromagnetic stirring, etc. The processing parameters of cooling slope casting are length, angle and the material of the inclined plate and their combinations, which usually affect the micro structural evolutions of the primary solid phase. In order to clarify the effect of the processing parameters on the evolution of the particle size, based on experimental investigation, Artificial Neural Network (ANN) was applied to predict the primary silicon crystals (PSCs) size of semisolid cast ingot via a cooling slope casting process of Al-20%(wt.%) Si alloy. The results demonstrated that the ANN, with 2 hidden layers and topology (4, 3), could predict the primary particle size with a high accuracy of 94%. The sensitivity analysis also revealed that material of the cooling slope had the largest effect on particle size.
M. Shahmiri, S. Murphy,
Volume 5, Issue 4 (Autumn 2008 2008)

Abstract: The microstructural features of the early stage of ordering of the intermetallic compound Pt2FeCu have been examined using optical and transmission electron microscopy in conjunction with X-ray diffraction technique. It was found that the compound has similar morphological alteration to that of FePt in which the ordering cannot be suppressed by rapid quenching. The early stage of ordering transformation was initiated at temperatures above the critical value of 1178 oC, by a homogeneous nucleation of the intermediate short range ordered particles and ultra rapid directional-induced heterogeneous growth (burst type). As the result of these combined mechanisms, twin –related ordered domains have been formed which in turn minimize the strains produced by ordering reaction in polycrystalline material. The individual grain was divided up by different sizes of twin-related ordered domain bonded with {101} habit planes.
B. Tolaminejad, A. Karimi Taheri, H. Arabi, M. Shahmiri,
Volume 6, Issue 4 (Autumn 2009 2009)

Abstract: Equal channel angular extrusion (ECAE) is a promising technique for production of ultra fine-grain (UFG) materials of few hundred nanometers size. In this research, the grain refinement of aluminium strip is accelerated by sandwiching it between two copper strips and then subjecting the three strips to ECAE process simultaneously. The loosely packed copper-aluminium-copper laminated billet was passed through ECAE die up to 8 passes using the Bc route. Then, tensile properties and some microstructural characteristics of the aluminium layer were evaluated. The scanning and transmission electron microscopes, and X-ray diffraction were used to characterize the microstructure. The results show that the yield stress of middle layer (Al) is increased significantly by about four times after application of ECAE throughout the four consecutive passes and then it is slightly decreased when more ECAE passes are applied. An ultra fine grain within the range of 500 to 600 nm was obtained in the Al layer by increasing the thickness of the copper layers. It was observed that the reduction of grain size in the aluminium layer is nearly 55% more than that of a ECA-extruded single layer aluminium billet, i.e. extruding a single aluminium strip or a billet without any clad for the same amount of deformation. This behaviour was attributed to the higher rates of dislocations interaction and cell formation and texture development during the ECAE of the laminated composite compared to those of a single billet

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