MICROSTRUCTURAL DEVELOPMENT IN A METAL-MATRIX COMPOSITE DURING THERMOMECHANICAL PROCESSING

Although a considerable amount of research on particulate reinforced m etal matrix composites (MMCs) has concentrated either on their primary processing, or on their failure while in service, little attention ha s been given to their mechanical and/or physical behavior during secon dary processing. Hence, there is only limited information available to facilitate the design of suitable thermomechanical processing schedul es for these alloys. However, in order to design an appropriate proces sing route, it is necessary to develop an understanding of the microst ructural development of both the matrix alloy and reinforcing particle s during hot deformation. This research investigated the effect of hig h temperature deformation on the microstructural development of the al uminum alloy 2618 reinforced with 17% SiC particles by volume. Particu lar attention was directed towards the fracture behavior of the reinfo rcing particles deformed under conditions of plane strain. Results fro m extensive quantitative metallography show that SiC particles can be significantly refined during thermomechanical processing. Additionally , at these elevated deformation temperatures, particles redistribute t hemselves within the matrix, resulting in a more homogeneous distribut ion. This behavior has been characterized using Dirichlet tessellation s. Finally, it is shown how the refinement and redistribution of the S IC particles can lead to the enhancement of the fracture-related prope rties.