Abstract
The influence of volume fraction of Al₂O₃ particles on fracture of the Cu-Al₂O₃ system is analysed by "in situ tensile test in SEM". It is shown, that tensile strain produces first micro-cavities on matrix-particle interfaces due to decohesion of particles from the matrix. The cavities grow and coalesce in the first place in the direction of rows of particles with growing strain. Cracks develop in both directions: along the rows and in the direction perpendicular to the rows, leading to final fracture. The deformation at fracture, elongation, is dependent on Al₂O₃ particle volume fraction. A model explaining the fracture mechanism is introduced.

Key words
SEM, fracture mechanism, dispersion hardening

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