Directional growth and characterization of Fe-Al-Nb eutectic alloys

The manufacturing of components for operation at high temperatures requires the use of metallic materials which can keep satisfactory mechanical and c hemical properties, even at temperatures beyond 1000 degrees C. An interest ing alternative to solve such a problem is the use of directionally solidif ied eutectic alloys. A potentially promising system for the manufacture of structural materials, and so far not totally studied, is the eutectic based on the Fe-Al-Nb system, which involves the (FeAl)(2)Nb phase and the FeAl solid solution. Eutectic samples from this system were directionally solidi fied in a vertical Bridgeman crystal growth unit. The objective of the expe riments was to determine the influence of the growth rate on the eutectic m icrostructure. The ingots obtained were investigated by using optical and e lectron scanning microscopy. At low growth rare, the eutectic microstructur e remained regular, even though it showed several types of microstructure d efects. As the growth rate was increased, a transition from lamellar to fib rous morphology was observed. (C) 1999 Elsevier Science B.V. All rights res erved.