The dislocation structure of a single-crystal γ+γ′ two-phase alloy after tensile deformation

The dislocation structures of an industrial single-crystal gamma + gamma' two-phase alloy DD3 after tensile deformation from room temperature to 1273K were studied by transmission electron microscopy. The strength of this alloy decreased with an increase in the temperature, and showed a strength peak at 1033K. At room temperature, the dislocations shearing the gamma particles were found to be 1/3[112] partial dislocations on the dodecahedral slip system [112]{111}. Some dislocation pairs on the cubic [110]{100} system that blocked the glide of dislocations were found at a medium temperature of 873K. As a result, dislocation bands were formed. Shearing of gamma' particles by 1/3[112] partial dislocations on the dodecahedral slip system [112]{111} was also found at this temperature. At the peak temperature of 1033K, because of the strong interaction between dislocations on the {111} and {100} planes, the extent of dislocation bands with high dislocation densities was extensive. The 1/3[112] partial dislocations on the dodecahedral slip system [112]{111} also existed. When the temperature reached the high temperature of 1133K, the range of dislocation bands was limited. The gamma' particles were sheared by [110] dislocation pairs on the octagonal [110]{111} system and the cubic [110]{100} system. At 1273K, the regular hexagonal dislocation networks were formed in the gamma matrix and at the gamma/gamma' interface. The Burgers vectors of the network were found to be b(1) = 1/2[110], b(2) = 1/2[1-10], b(3) = [100], and the last one was formed by the reaction of b(1) + b(2) --> b(3). Dislocations shearing the gamma' particles were found to be [110] dislocation pairs on the octagonal system [110]{111} and cubic slip system [110]{100} at 1273K. (C) Elsevier Science Inc., 1999. All rights reserved.