Rapid eutectic growth and applied performances of Fe[sbnd]Al[sbnd]Nb alloy solidified under electromagnetic levitation condition

Abstract

Electromagnetic levitation provides a containerless condition for materials processing, which is a desired technique to produce optimized microstructures and properties. In this paper, the large undercooling and rapid solidification of high-temperature Fe67.5Al22.8Nb9.7 alloy were realized by means of electromagnetic levitation method. The undercooling range from 13 to 150K was achieved, and the microstructure consisted of Nb(Fe, Al)2+(αFe) pseudoeutectic grains and a small amount of primary Nb(Fe, Al)2 phase. The eutectic growth velocity was measured and found to increase by nearly 4 times with enhanced undercooling. Both eutectic grain size and interlamellar spacing decreased more than 50% with the increase of undercooling. Owing to the structural refinement, the micromechanical property of eutectics in terms of Vickers microhardness was improved, whereas that of primary phase remained unchanged. The soft magnetism of the undercooled alloy was reduced according to the variation of hysteresis loops. Besides, the thermal expansion coefficient of this alloy increased by two times within the temperature range from 300 to 1573K, and the alloy density variation was determined accordingly.