발간논문

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Vol.39, No.10, 1108 ~ 1114, 2001
Title
Mechanical Behaviors : Superplastic Deformation and Load Relaxation Behavior of a Coarse - grained Iron Aluminide
하태권Tae Kwon Ha,송진화Jin Hwa Song,장영원Young Won Chang
Abstract
Superplastic deformation and high temperature load relaxation behavior of a coarse-grained iron aluminide have been investigated in this study. Iran aluminide with the composition of Fe-28 at.% Al was prepared and thermomechanically treated to obtain an average grain size of about 500 ㎛. A series of load relaxation tests was conducted at temperatures ranging from 600 to 850℃. The flow curves obtained from load relaxation tests were found to have a sigmoidal shape and to exhibit stress vs. strain rate data in a very wide strain rate range from 10^(-7)/s to 10^(-2)/s. Tensile tests have been conducted at 850℃ and at the various initial strain rates ranging from 3×10^(-5)/s to 1×10^(-2)/s to investigate the superplastic deformation behavior. The maximum elongation of ∼500% was obtained at the initial strain rate of 3×10^(-5)/s and the maximum strain rate sensitivity was Found to be 0.68. Microstructure observation through the optical microscopy and EBSD (electron back-scattered diffractometry) technique has been carried out on the deformed specimens and revealed the evidences for grain boundary migration and grain refinement to occur during deformation, suggesting the dynamic recrystallization mechanism. The activation energy was evaluated as 387 kJ/㏖ in the strain rate range from 10^(-4)/s∼10^(-2)/s, which is very close to that for creep deformation in Fe₃Al alloys.
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