Metal AMS
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53 - Understanding the macroscopic properties of the PBF-LB 17-4 PH steel by a set of microstructural investigationsliveira Melo


17-4 PH is a grade of stainless steel with numerous applications in medical, nuclear, chemical and aircraft industries. Over the last decade, great attention has been paid to this reliable engineering alloy elaborated by additive manufacturing (AM) processes, especially Powder Bed Fusion Laser Beam (PBF-LB) technique, given its compatibility with the complex elaboration context. Nevertheless, even if the AM processes are suitable for the elaboration of industrial components, there are still challenges to attain certain values of mechanical properties when comparing to the alloy elaborated by conventional processing routes. The present work searches to elucidate the connexion between microstructure and tensile as well as notch impact properties of the AM 17-4 PH steel. This relies on the comprehension of the mechanisms that operate within the occurring plastic deformation during those solicitations. As the 17-4 PH steel grade belongs to structural hardening alloys, several thermal treatments have been considered, leading to its softened condition. In addition, the properties of the material elaborated by AM have been compared to the wrought one, especially for impact resistance properties which are particularly low for AM 17-4PH steel. The thorough metallographic investigations rely first on a set a multi-scale analysis. Indeed, in the current case, the 17-4 PH is known to exhibit a complex microstructure consisting of a tempered martensite matrix with retained and reversed austenite as well as copper and niobium precipitates depending on the considered thermal routes. Such microstructural aspects are presented from a global point of view with the application of Light Optical Microscopy (LOM) and X-ray Diffraction (XRD) techniques to have an idea of the phase / constituent repartition at the micro-scale. To understand more precisely how the microstructure reacts to both static and dynamic loadings, advanced techniques have been employed. Electron Back-Scatter Diffraction (SEM-EBSD) and Electron Channelling Contrast Imaging (SEM-ECCI) were combined to estimate the local plasticity and how each mesoscopic constituent accommodates the plastic deformation. Scanning Transmission Electron Microscopy (STEM) has been employed to describe the response of the various precipitates.


CNRS, INRAE, Centrale Lille, UMR 8207—UMET—Unité Matériaux et Transformations, Université de Lille, Lille, France

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53 - Understanding the macroscopic properties of the PBF-LB 17-4 PH steel by a set of microstructural investigationsliveira Melo



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