On the microtwinning mechanism in a single crystal superalloy

Segregation-Assisted Plasticity in Ni-Based Superalloys

“…Barba et al [14] and Smith et al [2] have proposed a model to rationalize this phenomenon. In their models there is a local shift of chemistry from c 0 !…”

“…In this section, the model presented by Barba et al [14] for segregation-assisted growth of microtwins is extended for the case of CISFs/SISFs, CESFs/SESFs, and APBs. The mathematical model is summarized in Appendix A.…”

“…Then the mathematical problem presented here differs slightly from the real case but in any case, the values obtained here for APBs velocities represent a lower bound. For more details of the mathematical model, the reader is referred to the work of Barba et al [14] 1. Definition of model parameters The velocities for the different types of faults are obtained by imposing the effective segregated Cr and Co concentrations at the fault and the c 0 -phase nominal concentration, both obtained from the EDX analysis presented before.…”

“…The mathematical model proposed by Barba et al [14] for the case of Co and Cr partitioning-controlled growth of microtwins is used here. A schematic of the physical problem is shown in Figure 8(a).…”

“…Consequently, new nano-and micro-mechanical interpretations need to be advanced, for scientific benefit and technological effect. This paper is concerned primarily with the chemical segregation at the planar defects introduced by creep deformation in a prototype Ni-based superalloy at 800 C. In the alloy considered, the role of microtwinning in promoting creep deformation at such temperature has been proven [14] ; nonetheless, the factors promoting nucleation and propagation of such microtwins need much further clarification. First, experimental proof of chemical segregation to the different types of planar faults formed in the superalloy is presented.…”