ROLE OF COHERENT INTERPHASE BOUNDARIES ON DEFORMATION.

In some cobalt base alloys, which are nominally single phase fcc materials, the hcp phase can be easily formed, either by deformation and/or heat treatment, in sufficiently large volume fraction so as to affect mechanical behaviour. In this paper we examine the role of the coherent fcc-hcp interphase boundaries and twin boundaries on deformation. The emphasis is on the application of transmission electron microscopy to study dislocation accommodation at these interfaces in a Co-Cr-Mo alloy after room temperature and high temperature deformation. A mechanism of dislocation interaction at SIGMA equals 3 boundaries during high temperature deformation is proposed.