Mapping stress heterogeneity in single-crystal superalloys by novel submicron-resolved X-ray diffraction

Coherent precipitation, a common strengthening approach, is typically subjected to spatial non-uniformity due to microscopic segregation, leading to multi-scale stress heterogeneity. Such heterogeneity remains poorly characterized because unavailable local strain-free lattice parameters invalidate traditional diffraction-based stress measurement techniques. To overcome these limitations, we demonstrate a submicron-resolved synchrotron X-ray diffraction method to map coherency stress distribution based on the γ/γ′ lattice misfits in Ni-based superalloys. Assisted by finite element analysis, sub-dendritic stresses are deduced from heterogeneous coherency stresses, confirmed by the diffraction experiments. The methodology offers a comprehensive framework to assess stress heterogeneity at multi-scales for all coherent precipitation strengthened alloys. Impact statement This study marks the first successful quantification of stress heterogeneity at multi-scales in alloys strengthened by non-uniform coherent precipitation, even in absence of strain-free lattice constants.