The influence of Ti addition on fracture toughness and failure of directionally solidified LaB6–ZrB2 eutectic composite with monocrystalline matrix

Fracture toughness and failure mechanism of directionally solidified eutectic composites LaB6–ZrB2 and LaB6–(Zr0,9Ti0,1)B2 were investigated. The addition of Ti increases the cohesion strength of the matrix–fiber interface, causes redistribution of stresses in the whole composite, and thus influences the mechanism of crack propagation.Fracture toughness of composites was determined by Brazilian test. The central crack was introduced in the plane, parallel to the axis of the eutectic rod, in direction, perpendicular to the axis. Such experimental setup enables to investigate the interaction of crack with fiber–matrix interface and eliminates the effect of other factors on K1C.The present investigation shows that Ti additions to LaB6–ZrB2 result in up to 25% increase of fracture toughness of the composites.