Crack interaction with microstructure

Designing microstructure for damage tolerance requires a detailed understanding of how an advancing crack interacts with the microstructure (and sometimes modifies it locally) at multiple length scales. Advances in experimental techniques, such as the availability of well-controlled straining stages for optical and electron microscopes, the focused ion beam, electron backscattered diffraction, and nanoindentation, enable probing at these length scales in real time and through interrupted tests. Simultaneously, increasing computational power coupled with new computational methods, such as finite element analysis (FEA) incorporating cohesive elements at the continuum level, discrete dislocation methodology at the mesoscopic level, and coupled atomistic/continuum methods that transitions atomic level information to the mesoscopic level, have made it possible to begin addressing these complex problems. By reviewing crack growth in a variety of multiphase alloys including steels, titanium aluminides, Mo alloys, and nanocrystalline metals, we demonstrate various aspects of crack interaction with microstructure, and how these problems are being addressed through experiments and computations.