A Study of the Interfacial Stability of Ti/Al2O3, Ti3Al/Al2O3 and TiAl/Al2O3 Composite Materials

This thesis is a study of the interfacial stability of the Ti-Base metal matrix composites Ti/Al2O3, Ti3Al/Al2O3 and TiAl/Al2O3. Interfacial stability is discussed in view of the importance of thermodynamics and kinetics as the primary considerations which govern the type of stability observed. From a thermodynamics approach, the application of phase equilibrium diagrams is essential in the design of composite systems. A classification system, with reference to phase equilibrium, is used to describe the type of interfacial stability observed for the composites studied. In addition, electron-probe microanalysis, atom-probe field ion microscopy and X-ray diffraction results are used to establish Ti-Al-O phase relations for the temperature range 900-to-1250 deg C. The kinetics of interfacial stability is discussed with particular attention given to the kinetic considerations; diffusion path, phase formation sequence, steady-state layer growth and interface morphology. Kinetic results in the form of parabolic growth constants and calculated interdiffusion coefficients are presented.