Effects of thermal ε martensite content and deformation on damping capacity of a Co–32 wt.% Ni alloy

The damping capacity of Co–32 wt.% Ni alloy was investigated as a function of the amount of thermal and strain-induced ε martensite under non-magnetic and 900 Oe magnetic fields, respectively. The damping capacity of the Co–32 wt.% Ni alloy containing ε martensite without magnetic field consists of the magneto-mechanical damping capacity of mainly α phase, damping capacities of α and ε phases without magneto-mechanical damping effect. Under a magnetic field of 900 Oe, the more the thermal ε martensite mass fraction the higher the damping capacity. However, the damping capacity of the deformed Co–32 wt.% Ni alloy with the strain-induced ε martensite decreases with increasing deformation degree despite the increase in total ε martensite fraction, because the lattice defects like dislocations introduced during deformation act as barriers to movement of damping sources such as magnetic domain walls, stacking faults boundaries in both α and ε phases, and α/ε interfaces.