Microstructure-magnetic shielding development in additively manufactured Ni-Fe-Mo soft magnet alloy in the as fabricated and post-processed conditions

• Published in: Journal of alloys and compounds 2021-12, Vol.884, p.161112, Article 161112
• Main Authors: Mohamed, Abd El-Moez A., Sheridan, R.S., Bongs, Kai, Attallah, Moataz M.
• Format: Article
• Language: English
• Subjects: Crystal defects; Crystallography; Flux density; Grain orientation; Heat treatment; Hot isostatic pressing; Iron; Laser powder bed fusion; Lasers; Magnetic anisotropy; Magnetic properties; Magnetic shielding; Magnetism; Magnetization; Mechanical properties; Metallurgical analysis; Microstructure; Molybdenum; Mu-metal; Nickel base alloys; Optimization; Powder beds; Tubes
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.161112

•Ni-Fe-Mo soft magnets were 3D printed using laser powder bed fusion additive manufacturing technique.•The relation between the microstructural defects and the magnetic properties are studied.•After coercivity (Hc) optimisation, sample with lowest microstructural defects shows lowes Hc value (242A/m) was corresponding to the sample with the lowest microstructural defects that was built with laser energy density (E) of 4.68 J/mm2.•The highest magnetic shielding achieved value was 502, which represents 83% of the commercial magnetic shields. This study introduces a deep analysis, which correlates the metallurgical characters with the magnetic properties in laser powder bed fusion processed Ni-Fe-Mo, to produce 3D prototypes with maximum magnetic shielding performance for ultra-sensitive quantum-based systems. The study conducts a sequenced plan of optimising the magnetic properties via microstructure density control, controlling the magnetic anisotropy, before applying heat treatment (HT) and hot isostatic pressing (HIP) post-processes. This is also considering delivering effective mechanical properties. The magnetic properties optimisation was performed via laser parametric study, which found that the sample built with laser energy density E = 4.68 J/mm2 achieves the best soft magnetic and mechanical results due to the lowest defects. However, the obtained magnetic properties are still poor, due to the (001) rich grain orientation, which parallels the hard axis of magnetisation  in this alloy. It was found that tilting the crystallographic orientation of the as fabricated (AF) optimised condition with 45˚ and 35˚, with respect to the build direction, improves the soft magnetic properties, as these angles correspond to the easy axes of magnetisation and , respectively, allowing the grain orientation in the same directions. The magnetic properties are further promoted with HT and HIP post-processes application. The magnetic shielding results of hollow tubes, built with the same optimised condition, confirmed the magnetic behaviour of the bulk coupons, achieving 83% of the commercial magnetic shielding.