Eutectic Instability and Phase Selection of Al-Sm Alloys N. Wang 1 , S. David 2 , H. Walker and R. Trivedi Materials and Engineering Physics, Ames Laboratory USDOE, Iowa State University, Ames, IA 50011 1 Department of Applied Physics, Northwestern Polytechnical University, Xian 710072, China 2 Oakridge National Research Laboratory, Oak Ridge, TN E-Mail: trivedi@ameslab.gov (Received 30 June 2006 ; in revised form 20 November 2006) Trans. Indian Inst. Met. Vol.60, Nos. 2-3, April-June 2007, pp. 69-73 TP 2102 ABSTRACT Microstructure evolution over a wide range of growth rates has been examined in the Al-Sm system in which different microstructure selection, from eutectic to dendritic to amorphous material, with increasing growth rate can occur. Experiments were carried out for compositions between 11 and 25 wt.% Sm and the velocity was varied from 2x10 -4 to 635 mm/s. Low velocity studies were carried out using the Bridgman technique, whereas high velocity studies were carried by using the laser scanning technique. The maximum velocity for eutectic growth was determined, and the results were compared with the theoretical predictions. A transition from eutectic to α-Al dendrites was observed when the eutectic became unstable, and a coupled zone boundary on the Al side was determined. The present results were compared with those in the Al-Cu alloys, and the velocity at which the eutectic becomes unstable was found to be an order of magnitude smaller, which is related to the higher activation energy for diffusion in the Al-Sm system. Control of Monotectic Solidification by a High Static Magnetic Field H. Yasuda, I. Ohnaka * , B.K. Dhindaw 1 , T. Nagira, A. Sugiyama * , K. Umetani 2 , K. Uesugi 2 , A. Tsuchiyama 3 and T. Nakano 4 Department of Adaptive Machine Systems, Osaka University, Osaka, 565-0871, Japan 1 Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, West Bengal, India 2 Japan Synchrotron Radiation Research Institute, Hyogo, 679-5198, Japan 3 Department of Earth and Space Science, Osaka University, Osaka, 560-0043, Japan 4 Geological Survey of Japan, AIST, Tsukuba, 305-8567, Japan * Present address: Department of Entrepreneur Engineering, Osaka Sangyo University, Osaka, 574-8530, Japan E-Mail: yasuda@ams.eng.osaka-u.ac.jp (Received 30 June 2006 ; in revised form 20 November 2006) Trans. Indian Inst. Met. Vol.60, Nos. 2-3, April-June 2007, pp. 75-78 TP 2103 ABSTRACT Effect of magnetic field on the microstructure developed during the unidirectional solidification was investigated and the in-situ observation of the monotectic solidification was performed using synchrotron radiation X-ray for Al-10at%In hypermonotectic alloy. Coarse In rods and fine In rods could coexist during the unidirectional solidification when a magnetic field was not imposed. The static magnetic field exceeding several T promoted formation of the regular structure in which cylindrical In rods with the same diameter are regularly aligned in the growth direction. The in-situ observation showed that the coarse In-rich droplets that were continuously pushed by the Al solidifying front produced the coarse In rods. The continuous pushing prevented the selection of the rod spacing and resulted in the coexistence of the coarse and the fine rods.