Strain-induced martensitic transformations in tailored microstructures by L-PBF: In situ characterization via advanced neutron imaging

The possibility of controlling the microstructure in laser powder bed fusion (L-PBF) by locally changing the processing parameters, opens the possibility of building complex structures with tailored microstructures, leading to the development of smart materials. For metastable austenitic steels, the crystallographic texture strongly affects the TRIP effect. By employing L-PBF it is possible to locally engineer the microstructure to enhance or suppress the phase transformations. Here we quantitatively assess the transformation behavior of metastable stainless steel multitextured specimens manufactured by L-PBF under uniaxial tension quantifiting the formation of α′-martensite volume fraction in situ by employing polarization contrast neutron imaging (PNI). The results demonstrate a direct correlation between the local crystallographic texture of the specimens and the TRIP effect, providing valuable insights into the transformative potential of L-PBF in tailoring microstructures as well as the usefulness of PNI for characterizing complex structures.