High temperature thermo-mechanical and low cycle fatigue behaviors of DD32 single crystal superalloy

Abstract

Fatigue cycles decrease in the sequence of in-phase TMF (IP), isothermal low cycle fatigue (IF), out-of-phase TMF (OP) in the temperature ranges from 600°C to 900°C when the total strain amplitude is taken as the basis. However, fatigue life decreases in the sequence of IF, OP, and IP with the mechanical strain range as the basis. At lower strain amplitude, the fracture surfaces of OP present a mass of typical fatigue steps. Nevertheless, at higher strain amplitude in IP case the fracture surfaces with a lot of planar dimples are similar to those of high temperature creep test. The common deformation features of IP, OP, and IF are a network of dislocations at lower strains and well defined dislocation bands at higher strains.