INFLUENCE OF CU2O AND CUALO2 INTERPHASES ON CRACK-PROPAGATION AT CU ALPHA-AL2O3 INTERFACES/

In-situ crack-propagation experiments, in conjunction with thermochemi cal experiments, have been used to examine the role of discontinuous i nterphases on the fracture behavior of solid-state diffusion-bonded Cu /alpha-Al2O3 couples, ''Clean,'' interphase-free interfaces exhibit cr ack extension by brittle decohesion at the crack tip at an initiation fracture energy of similar to 125 J/m(2). Crack propagation is charact erized by an increase in the fracture energy with increases in the cra ck length (R-curve behavior), When interfacial chemical reaction produ cts are present, the crack growth is altered, depending on the charact eristics of the interphase, The presence of Cu2O needles results in pr eferential debonding along the Cu2O/Al2O3 interface. On the other hand , finer CuAlO2 needles visibly impede crack propagation and result in a higher interface initiation fracture energy (similar to 190 J/m(2)) than that of the interphase-free interface, The effects of the Cu2O an d CuAlO2 phases on the fracture energy are discussed.