발간논문

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Vol.37, No.4, 409 ~ 416, 1999
Title
Research Paper / Mechanical Behavior : Microstructure and Deformation Chraracteristics of Iconel 690 Alloy for Steam Generator Tubes ; ( 1 ) Precipitation Behavior of Carbides
안영철Young Cheol Ahn, 김희영Hee Young Kim, 홍순형Soon Hyung Hong, 한정호Jung Ho Han, 김정수Joung Soo Kim, 국일현Il Hiun Kuk
Abstract
The effects of thermal treatment on the microstructure evolution of Inconel 690 alloy were investigated. The carbides were precipitated mainly at grain boundaries by thermal treatment at 720℃. The intergranular carbidas were identified as M_(23)C_6 type and have cube-to-cube orientation relationship with the matrix. The size and shape of intergranular carbides were sensitively dependent on the thermal treatment time at 720℃. The average length and thickness of intergranular carbides increased with increasing thermal treatment time. The intergranular carbides showed inhomogeneous distribution after thermal treatment for 1hr, and were changed into semicontinuous after thermal treatment for 10hrs. The average distance between intergranular carbides showed the minimum value after thermal treatment for 10hrs due to the change of carbides from semicontinuous into discontinuous morphologies. The morphology of intergranular carbides did not affect the mechanical properties, such as yield strength, ultimate tensile strength and elongation. The solid solution temperature of intergranular carbides was measured as 1120-1140℃. The intergranular carbides hindered the grain growth during thermal treatment below the solution treatment temperature due to the Zener dragging of grain boundaries.
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