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The specimens of K465 superalloy were aged, respectively at 850, 950 and 1050 degrees C in order to investigate morphological changes of gamma' phase. The gamma' precipitates had the cubic shape and regular alignment with the positive and larger misfit before 800 h at 850 degrees C, 600 h at 950 degrees C, and 100 h at 1050 degrees C. When the tested alloy was aged from 600 to 1000 h at 950 degrees C and 100-300 h at 1050 degrees C, gamma' precipitates were coalesced and gradually lost the cubic morphology, and the magnitude of lattice misfit between gamma and gamma' phases was gradually decreased with the increase of aging time. The gamma' precipitates were elongated into plate with the negative misfit of smaller absolute value, and the misfit magnitude was decreased with the increase of aging time after 1000 h at 950 degrees C and 300 h at 1050 degrees C. The loss of the cubic shape of gamma' precipitates was caused by the reduction of misfit magnitude and the movement of dislocation into gamma' precipitates. The formation of elongated gamma' precipitates was related to the negative misfit of smaller absolute value and the dislocation networks and wall formed at the gamma'/gamma interfaces. (c) 2006 Elsevier B.V. All rights reserved. |
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