One-step additive manufacturing of Ni–Mn–Sn alloys with a large elastocaloric effect

Abstract

Ni–Mn–Sn metamagnetic shape memory alloys have garnered significant attention in solid-state refrigeration due to their highly tunable magnetic properties and large elastocaloric effects. However, their intrinsic brittleness hinders practical application. Laser powder bed fusion (L-PBF) additive manufacturing technology can overcome the machining difficulties of brittle alloys, enabling freeform geometrical design. Meanwhile, the rapidly cooled melt pool also facilitates the attainment of austenite functional phases. However, the elastocaloric effect of L-PBF alloys, especially for directly printed bulk materials without heat treatment, has not been systematically studied in Ni–Mn-based alloys. This work successfully obtained a rapidly solidified microstructure with austenite phases in Ni₄₅Mn₄₄Sn₁₁ alloys using a one-step L-PBF method without heat treatment. The relative densities of the L-PBF samples reached a maximum of 98.20%, with the entropy change values remaining stable in the range of 26 to 31 J kg⁻¹ K⁻¹. Compared to compression along the building direction, impressive and larger elastocaloric temperature changes (6.7 K) were achieved when compressing along the scanning direction due to the dominance of columnar grains and micron-sized defects. A maximum entropy change of 4.8 J kg⁻¹ K⁻¹ is achieved under an external magnetic change of 5 T. This work offers a simplified method for rapidly constructing solid-state refrigeration alloys with a large elastocaloric effect.