Slip bands in lamellar TiAl during high cycle fatigue microcompression by correlative total strain mapping, diffraction orientation mapping and transmission electron imaging.

• High cycle fatigue strains mapped by nanoscale resolution digital image correlation. • Fine bands of deformation in lamellar γ-TiAl alloy formed ∼50 nm from interfaces. • Unlike monotonic loading, high cycle fatigue strains remain highly localised. • Strain gradients develop along slip bands, increasing in magnitude with cycling. Microcompression testpieces of a lamellar γ-TiAl alloy were high cycle fatigued up to 105 cycles at stress ratios of 0.5–0.7, to maximum stresses above and below the yield stress. The localised deformation was studied by nano-scale digital image correlation strain mapping of a Pt patterned side-face of the pillars. With crystal orientation mapping, the fatigue deformation lines were found to locate at the γ/γ and γ/α 2 lamellar interfaces. The deformation lines were closely spaced slip lines in transmission electron imaging. Gradients of shear strain developed along the deformation lines, increasing in magnitude as cycling progressed. Extensive transverse twinning also occurred. [ABSTRACT FROM AUTHOR]