INTERNAL-FRICTION AND STRUCTURAL RELAXATION OF AMORPHOUS FE-MN-P ALLOYS

Measurements of internal friction and dynamic modulus have been carried out on amorphous Fe83-xMnxP17 (x = 9, 12, or 15) alloys in the temperature range 300-800 K, as a function of applied frequency, by a forced oscillation method. The characteristic transition temperatures and activation energies for crystallization were measured by differential scanning calorimetry (DSC). The viscous flow of the sample was measured using a thermomechanical analyzer (TMA) under continuous heating conditions. Internal friction increases rapidly with temperature starting from 450 K for 0.1 Hz, 474 K for 0.5 Hz, 486 K for 1.0 Hz, 511 K for 5 Hz, and 525 K for 10 Hz for the Fe74Mn9P17 specimen. It was found that the internal friction peak temperature was very closely the same as the steady state viscous flow temperature from the TMA curves for Fe74Mn9P17 and Fe68Mn15P17 but not for Fe71Mn12P17. It is assumed that the internal friction peak does not correspond to the glass transition temperature or crystallization temperature for these alloy systems. Two maxima in the free-volume fraction and two minima in the viscosity were also found for the samples which exhibit a 'mid-contraction' in their TMA displacement curves. The internal friction peak occurred at the steady state viscous flow temperature. This occurrence means that the origin of the internal friction peak is related to the viscous flow behavior and free-volume fluctuation for this alloy system.