The influence of transition phases on the damage behaviour of an Al/10vol.%SiC composite

In particle reinforced metal matrix composites (MMCs) such as Al/SiCp, there exist microscopic inhomogeneities due to the different elastic-plastic behaviour of the phases. As a result, stress and strain concentrations emerge at these inhomogeneities, the capacity for the deformation of one phase can be exceeded and local damage of the material and even macroscopic failure may occur. In order to investigate the damage behaviour of the ductile matrix, the damage parameter D, which was introduced by Rice and Tracey, and modified by Arndt et al., is used. Furthermore, cracking of the particles is the most commonly observed damage mechanism concerning the ceramic inclusions. In this case, a normal stress criterion is exploited to describe such kind of failure. As a third and more complex failure mechanism, delaminations between particles and matrix can take place. Frequently, there exists a transition phase between matrix and the inclusions with both, a ductile or a brittle material behaviour. To analyse the damage behaviour of the transition zone, both damage models (D-parameter and normal stress criteria) are applied into this region. Subsequently, this microstructure is modelled regarding the inclusion arrangement and the transition phase characteristics and parameter studies with respect to different transition interphase dimensions, material properties and critical failure stresses are performed. The damage behaviour of the microstructure is evaluated in consideration of the path and the amount of damage as well as stress-strain performance of the microstructure. In addition, residual stress effects on the damage behaviour are examined for various situations. In the light of these, the critical failure parameters that affect the damage behaviour of the microstructure are determined by comparing the results of several cases. It has been found, that transition phase material properties and dimensions possess an undeniable influence on the damage mechanisms of Al/SiCp composites. (c) 2006 Elsevier B.V. All rights reserved.