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

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 behavior. Strong magneto-structural coupling with Δ<i>M</i> = 93 A·m²·kg⁻¹ and a large Δ<i>S</i>_m of 23.1 J·kg⁻¹·K⁻¹ along with a <i>δT</i>_FWHM of 17.9 K and an <i>RC</i> value of 346.5 J·kg⁻¹ were achieved at 5.0 T in the sample sintered for 2 h. Additionally, a Δ<i>T</i>_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.基于粘结剂的增材制造（Binder-based additive manufacturing）在制备形状复杂且难以焊接的材料方面具有显著优势。然而，对于成分敏感的Ni-Mn-Sn-Co合金而言，引入粘结剂会给获得均匀微观结构带来挑战。针对熔融挤出增材制造Ni-Mn-Sn-Co合金时，封闭系统内粉末氧化与粘结剂脱除之间的权衡矛盾，本研究提出了一种一步式后处理烧结策略，通过在生坯（green parts）与共烧结材料（co-sintered materials）之间设置微小间距来解决该问题。仅需2小时直接密封烧结，即可获得室温下含有预马氏体的均匀各向同性微观结构。延长烧结时间后，样品仅出现少量锰元素烧损，马氏体转变行为未发生明显变化。对于烧结2小时的样品，在5.0 T磁场下实现了强磁结构耦合，其Δ<i>M</i> = 93 A·m²·kg⁻¹、超大磁熵变Δ<i>S</i>_m = 23.1 J·kg⁻¹·K⁻¹，相变半高宽温度区间<i>δT</i>_FWHM = 17.9 K，制冷量<i>RC</i> = 346.5 J·kg⁻¹。此外，在1.38 T磁场下直接测得绝热温变Δ<i>T</i>_ad为-1.99 K。本研究证明了可快速制备形状复杂、难以焊接且对成分敏感的Ni-Mn-X合金。