Experimental and Theoretical Aspects of Internal Friction Associated with the Melting of Embedded Particles

Internal friction associated with the volume change during melting was studied in an aluminum-16 wt% indium alloy. This alloy was processed to obtain microstructures consisting of nominally pure indium inclusions embedded in an aluminum matrix. Two sharp internal friction peaks were observed near the indium melting temperature of 156°C and both were associated with the formation and growth of liquid nuclei. A general theoretical model for the internal friction was developed which incorporates both the rates of phase deformation and the relaxation of the surrounding matrix. The proposed model considers the effect of the hydrostatic stress generated during melting that initially opposes the transformation. Matrix relaxation around the transforming particles resulting from vacancy flux and dislocation climb contributes an additional frequency dependence to the internal friction. Both the matrix relaxation and the internal friction peak height were found to be dependent upon thermomechanical processing. © 1993