Deformation-induced reorientation characterisation in P91 steel using double notch shear samples

To enhance the reliability of the design and improve the lifetime predictability of structural components, understanding deformation behaviour across multiple length scales is essential. This paper discusses the multiscale experimental characterisation of P91 steel using digital image correlation (DIC) and electron backscatter diffraction (EBSD) with the use of shear samples modified from ASTM B831 standard. Novel shear samples based on the ASTM B831 standard geometry have been modified to fit within a scanning electron microscope, allowing for both ex-situ and in-situ EBSD analysis. EBSD allowed the characterisation of deformation-induced crystal reorientation without requiring additional surface preparation. Deformation-induced reorientation to {1 1 0} planes in grains with Schmid factors over 0.4 has been observed empirically in P91 steel after 30 % shear strain. Geometrically necessary dislocation (GND) density increased linearly with shear strain in P91 shear samples and nearly doubled after 44 % shear strain.