Article ID: ISIJINT-2025-282
In an extensive flow of studies on material fracture, fracture mechanics has successfully established engineering standards for the safety evaluation of structural components. Vital difficulties in theories have been the management of the crack-tip stress singularity and the existence of incipient crack(s). Plasticity complicates fracture theories, and understanding the microscopic process of fracture is crucial for material design. This paper aims to shed light on the role of plasticity throughout the entire fracture process, remarking mostly brittle-like fracture, both in theory and experiment. Lattice deterioration due to plastic deformation increases potential energy, a key concept in deriving fracture criteria. Studies demonstrating the maturing of strain-induced lattice defects, primarily vacancy clustering, are reviewed to play a crucial role, operating as void source in fracture as a precursor to crack initiation.
Strain localization due to microstructural inhomogeneities are remarked to characterize the material's susceptibility to fracture. The extent of strain localization, coupled with external and local stresses, provides favorable fracture paths through crack nucleation and extension, as exhibited in fracture surface morphology. However, a single type of morphology does not specify a fracture event, and its continuous transition during crack extension suggests operation of an essentially common mechanism between seemingly different morphologies.
Lattice defects generated during plastic deformation persist into later stages, and environmental variations alter dislocation configurations, generating vacancies. As a method to assess the intrinsic material's susceptibility, detecting the progress of lattice deterioration in response to cyclic stressing is proposed.
