Linking Microstructures to Physical Properties

Advanced failure analysis using correlative mechanical microscopy

Unexpected metallurgical failure is expensive, either due to the additional costs of replacement parts and increased downtime, or due to more catastrophic consequences. Understanding the causes of failure is therefore a critical requirement for many applications, involving both microstructural characterisation to reveal the processes that result in part failure and mechanical testing to highlight potential structural weaknesses.

Both electron backscatter diffraction (EBSD) and energy dispersive X-ray spectrometry (EDS) in the scanning electron microscope (SEM) are routinely used for failure analysis, providing high resolution information about the local composition and structure of the material. Recent improvements in both EDS and EBSD are helping to deliver enhanced microstructural data, including better mapping of light elements (e.g. C, N and O) and the measurement of localised lattice distortion and dislocation content using new EBSD pattern matching techniques.

Linking these microstructural observations to the local physical properties requires high-precision mapping of mechanical properties (such as hardness or Young’s modulus) using MEMS-based nanoindentor systems. The correlation between the microstructural characterisation (using EDS and EBSD) and the mechanical properties (as measured using nanoindentation mapping) is called “Correlative Mechanical Microscopy” (CMM).