High Resolution Strain Measurements in a Polycrystalline Superalloy during Plastic Deformation: Slip Band Discontinuity Analysis
Résumé
Damage mechanisms in polycrystalline metallic alloys involve the accumulation of plastic strain at the sub-grain level. Measurements of the heterogeneous strain field that results from the complex grain boundary networks present in engineering alloys are combined with microstructural and orientation information to extract quantitative data on the deformation mechanisms. Digital image correlation (DIC) has been extended to higher resolution for analysis of discontinuities that evolve during fatigue and to measure strains at the sub-grain scale and below, where plastic strain localization can be directly correlated with physical slip bands. Strain fields have been measured in the polycrystalline nickel-base superalloy René 88DT to assess the deformation processes under monotonic and cyclic loading at room and intermediate temperature. A new analysis approach is presented to extract, for the first time, physical values of the magnitude of plastic localization and strain accumulation locally at the scale of the slip bands.