Pore-induced defects during thermo-mechanical fatigue of a fourth-generation single crystal superalloy
Zihao Tan, Xinguang Wang, J.C. Pang, Mingke Zou, Yan Tao, Xipeng Tao, Chenglu Zou, Yanhong Yang, Jide Liu, Jinlai Liu, Jinguo Li, Yizhou Zhou, Xiaofeng Sun
Abstract
Comparable investigation of pore-induced defects during in-phase (IP) and out-of-phase (OP) thermo-mechanical fatigue (TMF) were conducted on fourth-generation single crystal superalloy. It was discovered that recrystallizations and deformation twins would take shape near micro-pores at IP and OP cycling, respectively. High-resolution observation uncovered that the increasing a/6〈112〉 twinning dislocations and more frequent activation of 〈112〉{111} viscous slipping during OP-TMF accounted for twinning nucleation. Atom-scale mapping additionally disclosed the dual effect of Re, Co, and Cr in facilitating twinning formation and impeding of partial dislocations movement. It was deemed that the accumulation of pore-induced twins caused the premature fracture of alloy during OP-TMF.