Suppression and Recovery of Martensitic Transformation and Magnetism in Mechanically and Thermally Treated Magnetic Shape‐Memory Ni−Mn−Ga Melt‐Spun Ribbons

Abstract

As‐melt‐spun Ni50.2Mn28.3Ga21.5 ribbons are subjected to milling and subsequent annealing for various times. With progressing milling time, the martensitic transformation is gradually suppressed, magnetic moment deteriorates, whereas the crystal structure undergoes a body centered tetragonal (bct) into face centered cubic (fcc) change. High‐resolution transmission electron microscopy demonstrates a twin‐deformed zone in fcc powder particles, which works to improve circularity of as‐produced powders. Subsequent annealing of as‐milled powders restores martensitic transformation and magnetism, as well as it reverts the fcc into the original 5M structure. It is hence showcased that due to an allotropic transformation, brittle Heusler alloys are mechanically optimized for 3D printing without loss of their functional properties.