Abstract

The ability of high damping iron-chromium-aluminium alloys and coatings to absorb noise and vibrations has been investigated over a wide range of frequencies and amplitudes. The damping capacity was determined using a cantilever method based on the modal analysis technique of the flat beams and was found to be very sensitive to internal stress of specimens. Heat treatment usually enhanced the loss capability, but only an optimised annealing restored the maximum damping capacity. The influence of vibration amplitude evidenced by appearance of a maximum around ε = 10-4”, while the vibration frequency did not influence 'damping behaviour significantly. The position of the maximum damping was shifted towards lower strains with annealing time and temperature. The structure of magnetic domains was 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. Accordingly, the beneficial effect of annealing on damping capacity arises on the one hand from improved mobility of unpinned domain walls and on the other hand from growth of 90° domains considered as the principal responsible of damping. Addition of aluminium between 1-8 wt%. improved the damping values notably around 4 wt%.

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