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Material microstructure characterisation (License being explored)

A laser ultrasonic technique developed by Nottingham University – Spatially resolved acoustic spectroscopy (SRAS) –  is capable of precision measurements of the velocity of surface acoustic waves (SAWs) in a localised region on the surface of a sample. The SAW velocity is influenced by many factors, but for anisotropic, multi-grained materials (even if only very weakly anisotropic, such as aluminium), the dominant influence is due to microstructure which can be revealed in SRAS velocity images.  SRAS is especially useful for inspecting ‘difficult’ materials exhibiting anisotropic properties and coarse-grained microstructures e.g. titanium (below left) and austenitic welds (below right). The images are strikingly similar to Electron Backscatter Diffraction (EBSD) images; however, SRAS is quicker, requires less sample preparation and is applicable to large samples.

Subsequent technology transfer activities have led to the development of a portable demonstrator unit, trials in industrial applications and work with an equipment supplier involving an EngD research project aimed at bringing the method to market for advanced manufacturing applications. Monitoring the grain structure from production of the raw material through to the final part with feedback to the production process can have significant implications for  durability of the component.

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SRAS velocity image of titanium alloy sample 27x54mm (left) and austenitic stainless steel sample 30 x 60mm (right) for microstructure characterization