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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 features, texture and strengthening mechanisms of nanostructured AA6063 alloy processed by powder metallurgy
, Article Materials Science and Engineering A ; Volume 528, Issue 12 , 2011 , Pages 3981-3989 ; 09215093 (ISSN) ; Simchi, A ; Kim, H. S ; Sharif University of Technology
Abstract
Nanostructured AA6063 (NS-Al) powder with an average grain size of ~100. nm was synthesized by high-energy attrition milling of gas-atomized AA6063 powder followed by hot extrusion. The microstructural features of the consolidated specimen were studied by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques and compared with those of coarse-grained AA6063 (CG-Al) produced by hot powder extrusion of gas-atomized powder (without using mechanical milling). The consolidated NS-Al alloy consisted of elongated ultrafine grains (aspect ratio of ~2.9) and equiaxed nanostructured grains. A high fraction (~78%) of high-angle grain boundaries with average...
Effect of rapid solidification on the microstructure and mechanical properties of hot-pressed Al-20Si-5Fe alloys
, Article Materials Characterization ; Volume 60, Issue 11 , 2009 , Pages 1370-1381 ; 10445803 (ISSN) ; Vahidi, M ; Simchi, A ; Davami, P ; Sharif University of Technology
2009
Abstract
The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al-20Si-5Fe-2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 × 105 K/s and 5 × 107 K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 °C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated....