Change in Gamma Prime Morphology and Dislocation Substructures of Single Crystal Nickel-based Superalloy, CMSX-4, Prior-crept at 1273K-250MPa with Simple Aging

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The additional aging at 1273 K was done for the single crystal CMSX-4 pre-crept at interrupted the creep test at the strain of 0.01 at 1273 K-250 MPa. Changes in the γ morphology and in the dislocation substructure at the γ/γ interfaces with aging were investigated. The shape of γ precipitates in CMSX-4 pre-crept specimen at the creep at the strain of 0.01, remained still cuboidal. But by employing the additional aging to this interrupted specimen the shape of γ precipitates turned its shape to the rafted one perpendicular to the stress axis. A large number of the dislocations tangled were located at the γ/γ interfaces. By the additional aging, these dislocations were rearranged regularly with increasing aging time. However, the decrease in the dislocation density at the γ/γ interfaces with increasing aging time was not recognized. All dislocations at the γ/γ interfaces were defined by the six-kinds of the <110> Burgers vectors, irrespective to aging time. Consequently, dislocations at the γ/γ interfaces were regarded as not the misfit dislocations, but the mobile dislocations in the γ channels, and the formation of the rafted γ/γ structure might be correlated with the rearrangement of the dislocations.
2011-04-15