Book excerpt: This report describe the work done involving a study of high melting point intermetallic compounds. In order to study the deformation mechanisms of these materials at ambient temperatures, where they exhibit brittle behavior, it was proposed that ductile phase toughening should be employed so that some degree of plastic deformation might be induced in the brittle compounds. It was hoped that from a detailed analysis of defects in the deformed samples the various factors influencing the deformation mechanisms would become apparent. In the case of the higher temperature deformation experiments, a determination of the contribution of diffusive mechanisms to plastic deformation was to be made.