Abstract:
We demonstrate the refinement and uniform distribution of the crystalline dendritic phase by
friction stir processing (FSP) of titanium based in situ ductile-phase reinforced metallic glass
composite. The average size of the dendrites was reduced by almost a factor of five (from 24 μm
to 5 μm) for the highest tool rotational speed of 900 rpm. The large inter-connected dendrites
become more fragmented with increased circularity after processing. The changes in thermal
characteristics were measured by differential scanning calorimetry. The reduction in
crystallization enthalpy after processing suggests partial devitrification due to the high strain
plastic deformation. FSP resulted in increased hardness and modulus for both the amorphous
matrix and the crystalline phase. This is explained by interaction of shear bands in amorphous
matrix with the strain-hardened dendritic phase. Our approach offers a new strategy for
microstructural design in metallic glass composites.
