Ni-Mn-Sn shape memory Heusler alloys are known for their large caloric effects during the first-order phase transition from low temperature martensite to high temperature austenite, which makes the material interesting for caloric refrigeration [1]. The cyclic performance of the material can be enhanced by using the multiple stimuli cycle (magnetic field and compression stress) [2]. Challenging for the development of a good multicaloric material is the optimization of magneto- and elastocaloric effects on the one hand and of mechanical and cyclic stabilities on the other hand. Ni-Mn-Sn shows attractive magnetocaloric properties but the alloy is brittle and the polycrystalline condition is suffering from premature failure due to crack formation at grain boundaries upon cycling. One possibility to enhance the mechanical stability is grain boundary engineering utilizing additive manufacturing (AM). This could be demonstrated with the shape memory Heusler alloy Co-Ni-Ga. It was possible to process a textured alloy with excellent superelastic properties for a high number of cycles by Direct Energy Deposition (DED) [3]. Our goal is to transfer this knowledge about the manufacturing process to Ni-Mn-Sn Heusler alloy.
In this work, we present the material properties for the entire manufacturing process starting from the individual elements via powder production of the Ni-Mn-Sn alloy using gas atomization to the additive manufacturing by DED. For all the different steps the functional properties such as magnetization, Curie-temperature, martensitic phase transition, chemical composition and crystal structure were determined. We also determined the functional properties as a function of particle size distributions: 150-75 µm, 75-63 µm, 63-50 µm, 50-20 µm and smaller than 20 µm.

[1] T. Gottschall, K.P. Skokov, M. Fries, A. Taubel, I. Radulov, F. Scheibel, D. Benke, S. Riegg, O. Gutfleisch, Making a Cool Choice: The Materials Library of Magnetic Refrigeration, Adv. Energy Mater. 9 (2019) 1901322.
[2] T. Gottschall, A. Gràcia-Condal, M. Fries, A. Taubel, L. Pfeuffer, L. Mañosa, A. Planes, K.P. Skokov, O. Gutfleisch, A multicaloric cooling cycle that exploits thermal hysteresis, Nature Mater. 17 (2018) 929–934.
[3] C. Lauhoff, N. Sommer, M. Vollmer, G. Mienert, P. Krooß, S. Böhm, T. Niendorf, Excellent superelasticity in a Co-Ni-Ga high-temperature shape memory alloy processed by directed energy deposition, Materials Research Letters. 8 (2020) 314–320.