Revealing localized microstructure variations in additive manufacturing by neutron imaging

Victor Pacheco¹, Jithin James Marattukalam², Dennis Karlsson¹, Luc Dessieux^3,4, Tran Van Khanh⁵, Premysl Beran^6,7, Ingo Manke⁵, Nikolay Kardjilov⁵, Henning Markötter^5,8, Martin Sahlberg¹, Robin Woracek⁶

¹Department of Chemistry - Ångström Laboratory, Uppsala University, Box 523, SE-75120 Uppsala, Sweden; ² Department of Physics, Materials Physics, Uppsala University, Box 530, SE-75121, Uppsala, Sweden; ³ Physics Department, University of Tennessee, Knoxville, Tennessee TN 37996-1200, USA; ⁴ Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA; ⁵ Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), Hahn-Meitner-Platz 1, 14109 Berlin, Germany; ⁶ European Spallation Source ERIC, Box 176, 22100 Lund, Sweden; ⁷ Nuclear Physics Institute, Czech Academy of Sciences, 250 68, Řež, Czech Republic; ⁸ Bundesanstalt für Materialforschung und -Prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany

Laser powder-bed fusion (LPBF) has helped overcome some of the design constrains of conventional manufacturing methods and additionally, the technique has opened new paths for materials development. In particular, the possibility of tailoring microstructures, through laser scan strategies and parameters has attracted great interest in recent years. This microstructural control, is a unique characteristic of the LPBF method and one of its main advantages. However, complex scan strategies can produce unintended microstructural variations at a local level, which can easily remain unnoticed and give rise to misinterpretations.  
In this study, we employed diffraction contrast neutron imaging to reveal how the laser scan strategy can produce localized variations of the microstructure across cm-sized samples. In addition, through in-situ tensile testing, we show how the mechanical performance can be affected by these local changes.