HIGH DAMPING CAPACITY COATINGS FOR SURFACE VIBRATION CONTROL

The damping capacity Q(-1) of 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 l oss capability, but further annealing destroyed it drastically. The pl asma sprayed coatings was found to require more annealing to exhibit c omparable damping capacity to cast alloys of the same chemical composi tion. The variation of Q(-1) versus vibration amplitude first increase d rapidly, passed through a maximum around epsilon = 10(-4) and then d eclined relatively slowly to its initial values. The structure of magn etic domains were observed using the magneto-optical Kerr effect and t heir modification following to an applied stress or magnetic field was associated with different values of the damping capacity. The irrever sible movement of domain walls upon application of an external stress occurred suddenly and abruptly between two pinned positions.