Martensitic transformation and structural states in Ni44.0Mn43.5Sn12.5-xAlx (x = 1, 2, 3 at.%) magnetic shape memory alloys prepared by vacuum hot pressing

Heusler-type Ni-Mn-Sn magnetic shape memory alloys (MSMAs) that exhibit a significant magnetocaloric effect due to magnetic field-induced martensitic transformation (MT) represent promising applications within the field of solid-state cooling. However, their MT and physical properties strongly depend on the intricacies of the fabrication technology employed. In the current study, we demonstrated the advantages of the use of powder metallurgy in the preparation of MSMAs. Powders were vacuum hot pressed to fabricate Ni44.0Mn43.5Sn12.5-xAlx (x = 1, 2, 3 at.%) MSMAs. The way in which the Al influenced the martensitic transformation (MT) behavior, the structural characteristics, and the thermomechanical properties of the MSMAs was investigated. The findings revealed that the MT temperature increases significantly in response to Al doping, by approximately 20 K/1 at.%Al. Striking nanostructural states were revealed in the austenite phase, giving rise to the unusual stress-strain behavior of the alloys studied.