3D magnetic patterning in additive manufacturing via site-specific in-situ alloy modification

Abstract

Controlling the process-microstructure-properties relationship is at the heart of materials science. Thus in-situ compositional control in additive manufacturing has the potential to innovate present materials AM processing. We demonstrate in-situ alloy modification during laser powder bed fusion (LPBF) processing with the site-specific control of the para- and ferromagnetic properties in a high-nitrogen steel part fabricated by LPBF. Nitrogen can be selectively evaporated during the LPBF process by varying the volumetric energy density. The controlled evaporation of nitrogen stabilizes the ferromagnetic bcc phase at the expense of the paramagnetic fcc phase as shown by experiments and thermodynamic simulations. We demonstrate the feasibility to print complex magnetic structures by a 3D magnetic chessboard pattern comprised of non-ferromagnetic and partially ferromagnetic areas. The presented approach is applicable to all alloys where volatile elements affect the microstructure.