1273Kにてクリープ破断した単結晶Ni基超合金CMSX-4の転位下部組織(力学特性)

概要

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To clarify the feature of the rotation of the crystal lattice in the single crystal nickel-base superalloy, CMSX-4, during the creep deformation, the crystal misorientation across the interface of γ/γ' phase and that misorientation in the area of theγandγ' phase were investigated. Creep-rupture tests were conducted at 1273K, in the stress range of 200 to 320MPa. Microstructural observation by SEM indicated that the cuboidalγ' turns to the rafted one in all ruptured specimens. However, at the stresses higher than 250MPa, the interface between theγ/γ' was waved, while the interface betweenγ/γ' in the specimen crept at 200MPa remains straight one. The crystal misorientation across the interface ofγ/γ' phase and misorientations in the area of theγandγ' phase decreased with decreasing the stress. The average misorientation perpendicular and parallel to tensile directions across the interface ofγ/γ' phase were zero, independent of stress. At the lower stress side, the cuboidalγ' has regularly line up before rafting. However, at the higher stress side, the raftedγ' was formed after large creep deformation, and the rotation of the crystal lattice was also large, and the cuboidalγ' seemed to turn to the random direction. Consequently, it was suggested that the origin of the crystal misorientation in a single crystal nickel-base superalloy was theγ' phase rotated by subjecting the creep deformation.
2005-09-01