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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 17    No. 3    June 2007

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Effect of microstructures on superplasticity of Al-11%Si alloy
JIANG Jing-hua(江静华)1, MA Ai-bin(马爱斌)2, N. SAITO2,
A. WATAZU2, LIN Ping-hua(林萍华)1, Y. NISHIDA2

1. Department of Materials Science and Engineering, Hohai University,
Nanjing 210098, China;
2. National Institute of Advanced Industrial Science and Technology, 2266-98, Anagahora, Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan

Abstract:Three kinds of Al-11%Si (mass fraction) alloy samples with different processes were produced to investigate the effect of microstructures on its superplasticity. Among them, the as-ECAP sample pressed 16 passes has ultrafine grains (300 nm) and the finest secondary particles. The ECAP-T6 sample, with ECAP 16 passes followed by T6 treatment, has fine secondary particles (3 μm) but the largest grains (8 μm). Contrarily, the T6-ECAP sample, with T6 treatment followed by ECAP 16 passes, has ultrafine grains and the large secondary particles (7 μm). The tensile testing results show that the as-ECAP sample exhibits superplasticity at high strain rate of 5.75×10-1 s-1 due to its fine secondary particles and ultrafine grains. The ECAP-T6 sample, however, does not exhibit superplasticity at the same high strain rate of 5.75×10-1 s-1 because it has relatively large secondary particles and large grains. Remarkably, the T6-ECAP sample does not have superplasticity even at the lower strain rate of 1.15×10-1 s-1, attributing to its comparatively large secondary particles. When most secondary particles are larger than 7 μm, the high strain rate superplasticity could not be obtained even if this sample has ultrafine grains.

 

Key words: Al-Si alloy; microstructure; secondary particle size; superplasticity; grain size; metals and alloys

ISSN 1672-7029
CN 43-1423/U

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