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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 12    No. 4    August 2002

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Microstructure of Nb/Nb5Si3 in-situ composites
QU Shi-yu(曲士昱), WANG Rong-ming(王荣明), HAN Ya-fang(韩雅芳)

Beijing Institute of Aeronautical Materials, Beijing 100095, China

Abstract:The Nb-10Si (mole fraction, %) alloy was fabricated using the vacuum arc-melting method and heat-treated at 1850℃ and 1550℃ for 2~100h in Ar atmosphere. The microstructure of the alloy has been investigated using X-ray diffract ometry(XRD), scanning electron microscopy (SEM) equipped with X-ray energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM). The results show that 1550℃, 100h is an optimum heat-treatment condition to acquire the equilibrium Nb+Nb5Si3 two-phase microstructure. The microstructure of Nb-10Si alloy in the as-cast condition consists of continuous Nb3Si matrix and dispersed Nb particles, which implies that the alloy is in the metastable equilibrium state. In the case of 1850℃, 2h heat-treatment the Nb particles are coarsened evidently. How ever, in the heat-treatment condition of 1550℃ for 25~100h the growth of Nb particles is unconspicuous. After heat-treated at 1550℃, Nb3Si phase transforms into the equilibrium Nb5Si3 and Nb phase with the increase of heat-treatment time gradually. TEM observations reveal that the interface of Nb phase and Nb5Si3 phase is clean and some twins with about 10nm in width are found.

 

Key words: silicides; composites; heat treatment; microstructurev
CLC number:TG146.4

ISSN 1672-7029
CN 43-1423/U

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