Local characterization of stainless steel 17-4PH produced by material extrusion additive manufacturing: Influence of the post-treatment

This study focuses on the influence of porosities present in the stainless steel 17-4 PH made by material extrusion additive manufacturing (MEAM) process. A comparison is made at the sub-micron scale between an as-fabricated sample and a H900 post-fabrication heat treatment sample. To achieve such observations, gold nanoparticles (NPs) are used as markers in order to capture the evolution of the material behavior during an in-situ mechanical tensile test under a scanning electron microscope. The obtained strain maps allow to evidence strain concentrations and their evolutions regarding the microstructure and the applied post-treatment. The heat-treated sample reveals a change in size and number of porosities. The displacements of NPs during the test highlight the quantitative evolution of the crack initiations and the porosities growth, exposing a more homogenized strain evolution for the H900 sample compared to the as-fabricated one.