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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 18    No. 1    January 2008

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Synthesis and grain growth kinetics of in-situ FeAl matrix nanocomposites (Ⅱ): Structural evolution and grain growth kinetics of mechanically alloyed Fe-Al-Ti-B composite powder during heat treatment
REN Rong(任 榕), WU Yu-cheng(吴玉程), TANG Wen-ming(汤文明),WANG Feng-tao(汪峰涛), WANG Tu-gen(王涂根), ZHENG Zhi-xiang(郑治祥)

School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China

Abstract: Morphological changes, structural evolutions and grain growth kinetics of mechanically alloyed(MAed) Fe50Al50, Fe42.5Al42.5Ti5B10 and Fe35Al35Ti10B20 (mole fraction, %) powders were investigated by XRD and SEM, when being isothermally annealed at 1 073−1 373 K. The effect of different Ti and B addition on the grain growth of FeAl phase was also discussed. The results show that the nanocrystalline FeAl and in-situ TiB2/FeAl nanocomposite powders can be synthesized by subsequent heat treatment. Besides the relaxation of crystal defects and lattice stress, the transformation from Fe-based solid solution into B2-FeAl and TiB2 occurs upon heating of the MA-processed alloys. Although the grain growth takes place, the grain sizes of both FeAl and TiB2 are still in nanometer scale. The activation energies for the nanocrystalline FeAl growth in the three alloys are calculated to be 534.9, 525.6 and 1 069.6 kJ/mol respectively, according to kinetics theory of nanocrystalline growth. Alloys with different TiB2 contents exhibit unequal thermal stability. The presence of higher content TiB2 plays significant role in the impediment of grain growth.

 

Key words: FeAl; composites; heat treating; structural evolution; grain growth kinetics

ISSN 1672-7029
CN 43-1423/U

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