Measurement of interface strength in Al/SiC particulate composites

Fracture in particulate-reinforced metal-matrix composites is initiated by particulate cracking and interface decohesion, and crack propagation occurs through the matrix, particulate and interface. A ‘critical stress partition’ model is described which considers the proportions of matrix, particulate and interface for which the fracture stress is exceeded.

Tensile tests and microhardness measurements are reported for SiC/Al metal-matrix composites having particulate volume fractions of 0–20%. Measurements of the fractions of cracked and interface-debonded particulate before and after final fracture are combined with the fracture model to calculate the interface strength, σint′.

The values of σint′ obtained are 469 MPa for uncoated SiC particulate and 438 MPa for particulate coated with a thin layer of Al2O3 to prevent interface reaction. The tensile results indicate that the weaker interfaces promote interface debonding and increase percent elongation.