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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 16    No. 2    April 2006

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Evolution of grain structure in AA2195 Al-Li alloy plate during recrystallization
DU Yu-xuan(杜予晅), ZHANG Xin-ming(张新明), YE Ling-ying(叶凌英), LIU Sheng-dan(刘胜胆)

School of Materials Science and Engineering, Central South University, Changsha 410083, China

Abstract:The evolution of the grain structures in AA2195 Al-Li alloy plate warm-rolled by 80% reduction during recrystallization annealing at 500 ℃ was investigated by electron backscatter diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the elongated grain structures are caused by the lamellar distribution of recrystallization nucleation sites, being lack of large second phase particles (>1 μm), and dispersive coherent particles (such as δ′ and β′) concentrated in planar bands. The recrystallization process may be separated into three stages: firstly, recrystallization nucleation occurs heterogeneously, and the nuclei are concentrated in some planar zones parallel to rolling plane. Secondly, the grain boundaries interacted with small particles concentrate in planar bands, which is able to result in the elongated grain structures. The rate of the grain growth is controlled by the dissolution of these small particles. Thirdly, after most of small particles are dissolved, their hindrance to migration of the grain boundaries fades away, and the unrecrystallized zones are consumed by adjacent recrystallized grains. The migration of high angle grain boundaries along normal direction leads a gradual transformation from the elongated grains to the nearly equiaxed, which is driven by the tension of the grain boundaries.

 

Key words: AA2195 Al-Li alloy; microstructure evolution; elongated grains; equiaxed grains; recrystallization; second phase particles

ISSN 1672-7029
CN 43-1423/U

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