Fe-Ni-Mn alloys with an appropriate amounts of the elements show some peculiar properties such as high damping, shape memory and superelasticity. They have a similar structure consisted of γ, and α. Stacking faults formed into γ or twin formation within the martensite may be responsible for the properties.Amang materials tested, an Fe-5mass%Ni-15mass%Mn alloy cold worked by several percents was possessed of the best combination of these characteristics.