EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Diamond foils are known to be exceptionally strong yet brittle. One approach to make ceramic foils less susceptible to brittle fracture is to introduce interfaces into the material that provide pathways for crack deflection. In this study, we were able to produce strong yet tough diamond/metal laminates (DMLs) with an outstanding performance from freestanding diamond foils using a brazing process with an active AgTi braze. The mechanic response was characterized via three-point bending (3PB) where the laminates exhibit a stepwise fracture behavior. Crack deflection at the interface induces toughening in the laminates. The diamond/metal laminates exhibit with approx. 3.0 MJ/m3 more than twice the fracture energy of a monolithic diamond foil by maintaining 90% the stiffness and about 70% the nominal strength. Classical laminate theory (CLT) supports to assess the deformation and step-like fracture behavior of the diamond/metal laminates. We find that the diamond-to-metal interface plays a critical role: it must be strong enough to enable the transfer of shear stress, while being weak enough to deflect a crack.