논문 : 기계적 성질 ; 2 상 Ti-6Al-4V 합금의 크리프및 초소성 변형에 대한 미세조직학적 고찰
= Research Paper : Mechanical Behavior ; Microstructural Analysis on the Creep and Superplastic Deformation of Two-Phase Ti-6Al-4V Alloy
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초록
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A study has been made to investigate the microstructural aspects of phase/grain boundary sliding and its accommodation mechanism/mode during superplastic deformation in a two phase Ti-6Al-4V alloy. Tensile tests have been carried out at 600℃ and 900℃ using specimens of 3.2 and 10.6 μm grain sizes. Deformed microstructures have been analysed by transmission electron microscopy to understand the deformation mode, accommodation mechanism, and relative sliding rate of the phase boundary and grain boundaries, In the fine grain (3.2 μm) microstructure deformed at 600℃ and 900℃, dislocations were homogeneously distributed in the α-phase with low density implying that deformation mode follows an iso-stress model. However, the coarse-grain specimens (10.6 μm) reveal the planar slip behavior in the α-phase which indicates that the deformation mode is of a mixed type between iso-stress and iso strain rate mode. It is also considered that accommodation for phase/grain boundary sliding in the α and β phase mainly results from a dislocation activated process, The generation of boundary dislocations is more concentrated along α/β phase boundaries than the α/α grain boundaries, which confirms the sliding resistance of α/β < α/ α.
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