The ductility of metal matrix composites – Relation to local deformation behavior and damage evolution

Powder-metallurgy metal matrix composites (MMCs) with Al-6061 matrix and SiC-particles are analyzed by means of in situ tensile tests in the scanning electron microscope and automatic local deformation analyses. The particle size (10 and 100 μm) and the particle volume fraction (10% and 20%) are varied. For comparison the pure matrix material is also tested. The formation of the shear bands with increasing load is studied, and the differences in the shear band evolution in the different materials are worked out. Cracks are initiated by particle fracture and by matrix/particle decohesion. The crack tip opening displacements (COD) at the particle failure sites are determined, as well as the critical COD-values for particle cracks propagating into the matrix material. Qualitative relations between the global ductility of the MMCs and the deformation and damage behavior, both observed at the micro-scale, are worked out.