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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 12    No. 6    December 2002

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Thermal activation approaches to deformation mechanismsfor high Nb containing TiAl
base alloys
LIU Zi-cheng(刘自成), WANG Yan-li(王艳丽),
LIN Jun-pin(林均品),ZHANG Wei-jun(张卫军),
CHEN Guo-liang(陈国良)

State Key laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083, China

Abstract:The deformation mechanisms in a wide temperature range from room temperature to 1200K were investigated by thermal activation approach. Using observed instantaneous stress response to the strain rate jump (Δσtr), the activation volume Va, then the activation enthalpy ΔH, activation free enthalpy ΔG and activation entropy ΔS were calculated. The apparent activation energy of high temperature deformation is estimated to be 3.66eV, which is larger than the self-diffusion coefficient of binary TiAl (3.01eV). The dislocations at 1173K are generally curved or bowed, even helical-shaped dislocations. The climb of ordinary dislocations as well as twinning has greatly contributed to the plastic deformation. The CRSS at 1173K is estimated to be 180MPa. The higher resisting stress at both room temperature and elevated temperature might relate to the high Nb content of the alloy.

 

Key words:   TiAl; thermal activation approach; deformation mechanisms

ISSN 1672-7029
CN 43-1423/U

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