Microstructural development in a metal matrix composite during thermomechanical processing

Although a considerable amount of research on particulate reinforced metal matrix composites (MMCs) has concentrated either on their primary processing, or on their failure while in service, little attention has been given to their mechanical and/or physical behavior during secondary processing. Hence, there is only limited information available to facilitate the design of suitable thermomechanical processing schedules for these alloys. However, in order to design an appropriate processing route, it is necessary to develop an understanding of the microstructural development of both the matrix alloy and reinforcing particles during hot deformation. This research investigated the effect of high temperature deformation on the microstructural development of the aluminum alloy 2618 reinforced with 17% SiC particles by volume. Particular attention was directed towards the fracture behavior of the reinforcing particles deformed under conditions of plane strain. Results from extensive quantitative metallography show that SiC particles can be significantly refined during thermomechanical processing. Additionally, at these elevated deformation temperatures, particles redistribute themselves within the matrix, resulting in a more homogeneous distribution. This behavior has been characterized using Dirichlet tessellations. Finally, it is shown how the refinement and redistribution of the SIC particles can lead to the enhancement of the fracture-related properties.