EBSD analysis of creep deformation induced grain lattice distortion: A new method for creep damage evaluation of austenitic stainless steels

Abstract

Creep damage of austenitic stainless steels was evaluated by Electron Back-Scattered Diffraction (EBSD) analysis of creep deformation induced grain lattice distortion in this research. Based on the existing work of plasticity characterization by EBSD misorientation parameters, we used the grain lattice distortion parameter “Grain Reference Orientation Deviation (GROD)” obtained from EBSD analysis to estimate the creep strain εcreep of austenitic stainless steels by their linear correlation εcreep=(7.2∙GROD−2.4)% independent of creep conditions (stress σ0 & temperature T) and average grain size DGrain. Then the creep damage ratio (creep time fraction t/tr) was further evaluated from the estimated creep strain εcreep by constitutive equation describing the εcreep~t/tr creep curve, which takes the influence of creep conditions (σ0,T) into consideration. Compared with the previous work, this research developed a quantitative creep damage evaluation model with EBSD misorientation parameter GROD as input, creep damage ratio t/tr as output, and creep conditions (σ0,T) as environmental parameters. The final accuracy of the creep damage ratio evaluated by this new model can reach up to ± 30%.