High Damping Capacity Coatings for Surface Vibration Control

Abstract
The damping capacity Q^-1of a number of Fe-16%Cr alloys containing (0 - 6)%Al and (0 - 4)%Mo has been investigated and compared to that of thermally sprayed coatings. The magnetomechanical hysteresis loss was determined using a cantilever method and based on the modal analysis technique of flat beam samples. Heat treatments usually enhanced the loss capability, but further annealing destroyed it drastically. The plasma sprayed coatings was found to require more annealing to exhibit comparable damping capacity to cast alloys of the same chemical composition. The variation of Q^-1 versus vibration amplitude first increased rapidly, passed through a maximum around ε=10^-4 and then declined relatively slowly to its initial values. The structure of magnetic domains were observed using the magneto-optical Kerr effect and their modification following to an applied stress or magnetic field was associated with different values of the damping capacity. The irreversible movement of domain walls upon application of an external stress occurred suddenly and abruptly between two pinned positions.