Martensitic transformation, ductility, and shape-memory effect of polycrystalline Ni56Mn25-xFexGa19 alloys

Buttons of high-temperature shape-memory alloy Ni56Mn25-xFexGa19 were prepared by arc melting under argon atmosphere. The specimens were hot rolled to 1 mm. plates, and their martensitic transformation behaviors, ductilities, and shape-memory effects were investigated through differential scanning calorimetry and bending tests. It was found that the brittleness of polycrystalline Ni2MnGa was ameliorated through introduction of a ductile phase by Fe addition. Ni56Mn17Fe8Ga19 alloy shows great potential as a practical high-temperature shape-memory alloy with martensitc transformation start temperature above 200 degrees C. It can bear strain of 6 % before fracture in bending tests and shows a maximum reversible strain of 3.5 %.