Meaning
Material design and processing strategies used to prevent the formation of microscopic fractures during fabrication or operation. Mitigating these small defects is necessary to preserve the mechanical strength and hermeticity of advanced materials. This methodology addresses the internal residual stresses that arise from thermal expansion mismatches or phase transformations.
Stress Management
Thermal transitions during the cooling of multi-phase materials generate localized tension that can exceed the tensile strength of the matrix. Active microcrack suppression involves adjusting the cooling schedule and refining the grain size to distribute the residual strain more evenly throughout the microstructure. Smaller grain sizes limit the maximum possible length of a crack nucleus, which increases the stress required to propagate a defect.
Additionally, incorporating a secondary phase that undergoes stress-induced phase transformation can arrest growing cracks by exerting compressive forces at the crack tip.
Process Calibration
Dilatometry runs evaluate the expansion differences between phases to determine the optimal firing temperatures. Adjusting the composition based on these runs minimizes the internal strains generated during sintering.
Performance Outcome
Eliminating microstructural fractures increases the reliability of components under mechanical load. It also prevents the entry of moisture and corrosive agents, which extends the operating life of the assembly.
