3D characterization of magnetic phases through neutron polarization contrast tomography

•3D mapping of α′-martensite phase fractions in iron-based additively manufactured lattice structure specimens subjected to varying relative compression strains was demonstrated utilizing polarization contrast neutron tomography.•The study revealed a direct correlation between the compressive deformation, in particular at the strut intersections of the lattice structure, and the formation of α′-martensite, consistent with previous research that used digital correlation image analysis to reveal local strains.•The cross-shaped struts connecting the lattice structure, where the smallest compressive strains were found, were the least affected by martensitic transformation.•The exceptional sensitivity of the method to low martensitic phase fractions makes it a robust alternative to conventional techniques like e.g. neutron diffraction, which struggles to reliably detect such low phase fractions.