Fracture toughness and corrosion behaviour of infiltrated Al2O3|P – Steel composites

In the present study, the fracture toughness and the corrosion behaviour of particle reinforced alumina–steel composites were investigated. Composites, only differing in their type of matrix steel, were produced by Ti-activated pressureless infiltration. The aim was to clarify the influence of the matrix phase on the electrochemical properties as well as on the fracture toughness of the composites. Results show that the corrosion resistance of the composite mainly depends on the steel matrix. The processing history of the matrix steel is determining. Melt-processing decreases the corrosion resistance. All composites exhibit failure-tolerant behaviour. Though, local differences in the matrix plasticity on the micro-scale have been observed. Failure occurs primarily through Al2O3-particles. The increase in resistance against crack propagation, from about 8 to more than 30 MPa m1/2 after 1 mm crack extension, is attributed to the metallic matrix phase remaining intact behind the propagating crack front.