|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Materials for High Temperature Applications: Next Generation Superalloys and Beyond
||Sources of Creep Dislocations in Ni-base, Single Crystal Superalloys Revisited
||Farangis Ram, Zhuangming Li, Zailing Zhu, Masood Hafez Haghighat, Stefan Zaefferer, Dierk Raabe, Roger Reed
|On-Site Speaker (Planned)
The origin of creep dislocations in Ni-base, single-crystal superalloys at intermediate stress and temperature regimes is revisited. Using cross-correlation EBSD, subgrain boundaries in uncrept state were mapped and quantified. They accommodate lattice rotations of below 0.2°. Using electron channeling contrast imaging (ECCI), we found that although subgrains emit creep dislocations, they only account for a small number of creep dislocations that are in their close vicinity. In contrast, large amounts of dislocations were observed to develop far away from any interface. Discrete Dislocation Dynamics (DDD) simulations showed that the major sources of creep dislocations are isolated, individual dislocations in the uncrept material. They are homogenously spread in small quantities 10<SUP>11</SUP> m/m<SUP>3</SUP> far from subgrain boundaries before creep begins and are activated after activation of dislocations in subgrain boundaries. Once activated, they emit avalanches of creep dislocation into boundary-free regions and increase the dislocation density by two orders of magnitude.