Disorder-order transformation in Fe-50 %Co fabricated via laser powder bed fusion

• Published in: Additive manufacturing letters 2023-12, Vol.7, p.100174, Article 100174
• Main Authors: Nandwana, Peeyush, Fancher, Chris M., Kannan, Rangasayee, Babuska, Tomas F., Krick, Brandon, Kustas, Andrew B.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Fe-Co; Order-disorder; Phase transformations
• ISSN: 2772-3690; 2772-3690
• DOI: 10.1016/j.addlet.2023.100174

•Laser powder bed fusion suppresses the brittle B2 phase by retaining the metastable BCC A2 phase in the equiatomic Fe-Co alloy.•The suppression of the ordered B2 phase can make these alloys processable in near net shape forms.•Neutron diffraction shows that ordering occurs via classical nucleation and growth when the disordered as-fabricated material is heated.•During cooling, post heat-treatment, ordering occurs via a combination of homogeneous ordering and classical nucleation and growth. Fe-Co alloys are an important class of soft magnetic materials that often pose challenges in their fabrication because of the brittle B2-ordered phase. We show that laser beam powder bed fusion (PBF-LB), owing to its rapid cooling rates, offers an avenue for the fabrication of these alloys by suppressing the disorder →order phase transformation at room temperature. We use neutron diffraction to understand the phase transformations in a Fe-50 %Co alloy fabricated via PBF-LB. We report that the disorder→order phase transformation in this alloy occurs concurrently via homogeneous ordering and classical nucleation and growth.