Unidirectional Solidification of a Nbss/Nb5Si3 In-Situ Composite
The directionally solidified specimens of Nb-13.52 Si-22.60 Ti–6.88 Hf–2.54 Cr–2.24 Al alloy were prepared in an electron beam floating zone melting furnace at the withdrawing rate of 0.1, 0.3, 0.6, 1.0, 2.4 and 6.0 mm/min. All the primary Nb solid solution (Nbss) columns, Nbss + (Nb)3Si/(Nb)5Si3 eutectic colonies and divorced (Nb)3Si/(Nb)5Si3 plates or chains align well along the longitudinal axis of the specimens. With increasing of the withdrawing rate, the microstructure is gradually refined, and the amount of Nbss + (Nb)3Si/(Nb)5Si3 eutectic colonies increases. Both the room temperature ultimate tensile strength σb and fracture toughness KQ are improved for the directionally solidified specimens. The tensile fracture occurs in a cleavage way.
Z.Y. Zhong, H. Saka, T.H. Kim, E.A. Holm, Y.F. Han and X.S. Xie
X.P. Guo et al., "Unidirectional Solidification of a Nbss/Nb5Si3 In-Situ Composite", Materials Science Forum, Vols. 475-479, pp. 745-748, 2005