MICROSTRUCTURAL ASPECTS AND MECHANISM OF THE C49-TO-C54 POLYMORPHIC TRANSFORMATION IN TITANIUM DISILICIDE

Microstructural study of the C49-TiSi2 to C54-TiSi2 polymorphic transformation has been performed to elucidate microstructural evolution and possible mechanism of the phase transformation. It has been shown that the nucleation of the C54-TiSi2 is heterogeneous, and preferentially takes place at triple grain junctions or grain boundaries. The interphase interfaces between C49 and C54 disilicides are often ragged with incoherent characteristics. The growth of the C54 phase is found to proceed by advancing the highly mobile incoherent interfaces in all directions toward the heavily faulted C49 phase. No rigorous orientation relationships are found between the two phases. The microstructural features of the transformation bear some massive characteristics. © 1995 American Institute of Physics.