材料期刊网

An investigation of dislocation structure in a single crystal nickel-base superalloy during low cycle fatigue (LCF) at 760-degrees-C has been conducted. Dislocation bands are found to be produced first in the matrix in some defined directions. With an increase in cycle numbers, there is an increase in dislocation density in the bands and a decrease in the spacing between the bands, leading to the formation of the dislocation walls or cells. Sometimes, three-dimensional (3-D) networks are formed also by the interaction between two sets of parallel dislocations. The Burgers vectors of the dislocations in the network are 1/2 <110>. Clustering of dislocations eventually occurs at gamma'/gamma-interfaces because of the obstruction of the gamma'-particles to moving dislocations. Most of the dislocations observed in the gamma'-phases are in the form of superdislocations. Dislocation shearing through the gamma'-phase was found occasionally. Reprecipitation of gamma'-phase induced by strain was also observed in the present study.