Rapid preparation of Ni–Mn–Sn–Co lattice through material extrusion additive manufacturing and sintering

Binder-based additive manufacturing is considerably advantageous for the production of hard-to-weld materials with complex shapes. Nonetheless, the incorporation of a binder poses challenges in achieving a homogeneous microstructure for composition-sensitive Ni–Mn–Sn–Co alloys. To address the trade-off between powder oxidation and binder removal in a closed system in the case of material extrusion additively manufactured Ni–Mn–Sn–Co alloys, this study proposes a one-step post-treatment sintering strategy with a small separation between the green parts and co-sintered materials. A homogeneous isotropic microstructure with premartensite at room temperature was obtained after only 2 h of directly sealed sintering. When the sintering time was increased, samples showed a slight loss of Mn, without any significant change in the martensitic transformation behaviour. Strong magneto-structural coupling with ΔM = 93 A m² kg⁻¹ and a large ΔS_m of 23.1 J kg⁻¹ K⁻¹ along with a δT_FWHM of 17.9 K and an RC value of 346.5 J kg⁻¹ were achieved at 5.0 T in the sample sintered for 2 h. Additionally, a ΔT_ad of −1.99 K was directly measured at 1.38 T. This research shows the possibility of rapidly fabricating hard-to-weld and composition-sensitive Ni–Mn–X alloys with complex shapes.