Anomalous martensitic transformation and good ductility in all-d-metal Cu2Mn-based Heusler shape memory alloys from first-principles prediction

The inherent brittleness of conventional Heusler shape memory alloys degrades their fatigue life and serviceability, posing a significant challenge for their utilization in energy-efficient and environment-friendly solid-state refrigeration. Herein, the anomalous martensitic transformation (MT) and good ductility in all-<i>d</i>-metal Cu₂Mn<i>Z</i> (<i>Z</i> = Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Re, Os, Ir, and Pt) Heusler alloys have been systematically predicted using first-principles calculations. Most of them can undergo MTs and exhibit larger transformation strains, higher transition temperatures, and better ductility compared to Ni₂MnTi. Cu₂MnTi and Cu₂MnNb alloys demonstrate even stronger multicaloric effects. Hydrostatic pressure and magnetic disorder can further facilitate the transformations. A face-centered cubic phase may precipitate in the alloys with <i>Z</i> = V, Rh, and Ir, enhancing their ductility. These findings provide valuable guidance for their optimized design and application as magnetic shape memory alloys and multicaloric materials.