THE EFFECT OF PARTICLE DISTRIBUTION ON DAMAGE FORMATION IN PARTICULATE-REINFORCED METAL-MATRIX COMPOSITES DEFORMED IN COMPRESSION

Image analysis results are reported on the generation of damage in par ticulate reinforced metal matrix composites during compressive deforma tion. The technique allows the automated collection of data on the inc idence of particle fracture and void formation in the matrix as a func tion of important microstructural parameters such as local particle vo lume fraction and particle size. There is a strong relationship betwee n damage and the local volume fraction of the reinforcement proving th at damage formation is accentuated in regions of particle clustering. With the SiC reinforced materials examined, there was observed to be a change in dominance of damage mechanism from particle fracture at low local volume fractions to void formation in the matrix within strongl y clustered regions. The results are compared with finite element (FE) modelling of the compressive deformation of clustered particles using a simple cluster of equi-spaced particles. The FE results suggest tha t plastic flow is generally inhibited in clustered regions. In certain highly clustered configurations shielding is such that flow does not occur in the heart of the cluster even at high levels of average plast ic strain. The modelling suggests that the change in dominance of dama ge mechanism is related to the dramatic increase in tensile hydrostati c stresses in the matrix with higher levels of particle clustering.