In situ fracture observations of distinct interface types within a fully lamellar intermetallic TiAl alloy

Abstract

Intermetallic γ‐TiAl‐based alloys are commonly used as structural materials for components in high‐temperature applications, although they generally suffer from a lack of ductility and crack resistance at ambient temperatures. Within this study, the process‐adapted 4th generation TNM+ alloy, exhibiting a fully lamellar microstructure, was examined using notched micro‐cantilevers with defined orientations of lamellar interfaces. These configurations were tested in situ using superimposed continuous stiffness measurement methods during loading with simultaneous scanning electron microscopy observations. Subsequently, the video signal was used for visual crack length determination by computer vision and compared to values calculated from in situ changes in stiffness data. Applying this combinatorial approach enabled to determine the J‐integral as a measure of the fracture toughness for microstructurally different local crack propagation paths. Thus, distinct differences in conditional fracture toughness could be determined from 3.7 MPa m1/2 for γ/γ‐interface to 4.4 MPa m1/2 for α2/γ‐interface. [Figure not available: see fulltext.].