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Effect of cooling rate on microstructure and high temperature stability of rapidly solidified Al-Fe-V-Si alloys

Recently, AI-Fe-V-Si alloys have received more attention owing to their high temperature stability associated with vanadium rich precipitates and silicides. In this work, a series of alloys was prepared and processed by melt spinning and gas atomisation to observe the effect of solidification rate on crystal structures existing in both as cast and heat treated conditions. This study covers their microstructural examination and crystallography. The composition of these alloys was Al-(6.8-7.8)Fe-( 1.0-3)V-(1.6-2.2)Si and the ribbons and powders produced were examined by SEM and TEM. Investigations revealed that most of the rapidly solidified ribbons and powders consisted of a cellular structure with cubic spherical dispersoids and quasicrystalline i phase spheroids. The proportions of these phases were found to be dependent on section thickness and cooling rate of the products. More i phase spheroids were observed in sections of melt spun ribbons and coarse powders. After heat treatment at 300, 400, and 500 degrees C, the sizes of these dispersoids were detected to be two or three times the original as cast sizes. PM/0803 (C) 1999 IoM Communications Ltd.