Meaning
Mode of failure where the fracture line passes directly through the body of the individual metallic grains rather than along the grain boundaries characterizes this path. Observing transgranular cracking typically points to mechanisms involving stress corrosion or fatigue in specific alloy systems. The resulting cleavage looks like a straight line across the microstructural mosaic, signaling an environment where the internal grain is weaker than the boundary.
Mechanism Path
Fracture advances along primary crystallographic planes as energy dissipates through the lattice. For transgranular cracking to occur, the material must encounter high stress levels combined with an aggressive corrosive agent. This pattern differs visually from intergranular paths which look like branching veins between crystals.
Forensic Audit
Scanning electron microscopes provide the primary tool for identifying this specific mode during a failure analysis. When transgranular cracking is found, investigation focuses on the total mechanical load experienced during operation. Readiness audits include checking if the correct tempering sequence was used during initial manufacture.
Failure Prevention
Mitigation involves reducing the tensile forces or removing the specific ions that catalyze the crack growth. If transgranular cracking appears early in the testing of a prototype, the design capability must be restructured to lower internal stresses. Total life of the component depends on keeping load cycles shallow.
