Microcantilever Fracture Tests on Eutectic NiAl–Cr(Mo) In Situ Composites

Abstract

Lamellar eutectic NiAl–Cr(Mo) alloys show an increased fracture toughness due to different toughening mechanisms. These mechanisms result from the fibrous or lamellar microstructure of the two constituting phases α‐Cr(Mo) and β‐NiAl. However, the fracture toughness of the individual phases and the evolution from early crack growth to the toughening mechanisms have not yet been systematically studied. Herein, bending tests on focused ion beam (FIB)‐notched microcantilever beams are used to characterize the small‐scale fracture properties. The micromechanical investigations reveal that the fracture toughness of the α‐Cr(Mo) phase () is much higher than the fracture toughness of β‐NiAl (). Larger cantilevers in the crack arresting orientation show an enhanced fracture toughness with up to , which is still lower than the one of macroscopic experiments. This is attributed to the small interaction volume of the crack, which hinders the full exploitation of potential extrinsic toughening mechanisms.