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KUM, Dong Wha,Kang, Hyung 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.11
Small amount of aluminum addition to ultrahigh carbon steels (UHCS) leads to finer grain size during the established thermomechanical processing, and is known to improve the superplasticity of the steels. However, the effect of Al on the grain refinement in the hyper-eutectoid steels during thermomechanical processing is not well recognized and has never been quantitatively documented. Up to 5wt% aluminum was added to 1.2∼1.5wt%C steels and its influence on microstructural refinement has been studied. That is, the formation of proeutectoid carbide, austenite grain size, pearlite colony size, interlamellar spacing, equiaxed ferrite grain size and carbide particle sizes as a function of the Al-content were determined after hot-warm working plus an isothermal rolling or the divorced eutectoid transformation with associated deformation. Fine grain microstructure consisting of less than 1㎛ ferrite grains has been achieved by small Al-addition. It has been demonstrated that the dilute Al-alloying enhances the superplasticity of the UHCS: the optimum strain-rate has shifted to the faster rate region(at 800℃) and the tensile elongation of 545% has been observed at an initial strain-rate of 8.3×10^(-2)sec^(-1).
Al 의 첨가가 UHCS 의 펄라이트 판상간격에 미치는 영향
이동원,안재환,금동화 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.12
The effect of Al addition on the interlamellar spacing of pearlite in ultra high carbon steels (UHCS) has been investigated. 0.32∼1.75wt%Al were added to 1.2%C-1.5% Cr-UHCS. Isothermal pearlitic transformation experiments were performed at undercoolings of 50℃, 100℃ and 130℃ below the eutectoid transformation temperature. When transformed at undercoolings of 100℃ and 130℃, the interlamellar spacing of pearlite decreased with Al contents. This fact resulted from the decrease of interfacial energy due to the reduction of lattice mismatch between ferrite and cementite by Al partitioning. However, at the undercoolling of 50℃, the interlamellar spacing was independent of Al contents due to dominant Cr partitioning.