PhD student, 2016 intake

University: Imperial College London

Sponsor: BIAM

Background: Undergraduate 2010 and Master 2013, Xi’an Jiaotong University, China

Many high performance safety-critical components are being made from large-grain polycrystalline materials. Grain size and shape have a significant effect on their mechanical behaviours, e.g. yield, fracture and fatigue strength, thus it is of great importance to measure these microstructure parameters to achieve quality control.

A number of methods such as metallography and electron backscatter diffraction can be used for grain sizing, but they are quite limited to surface or thin-layer evaluation and are destructive when applied to volume characterization. Ultrasound, however, provides potential for non-destructive characterization of grain size and shape without the need of careful surface preparation and sample sectioning. Grain boundaries scatter ultrasonic waves due to the misalignment of crystallographic orientations between neighbouring grains, and the scattering-induced attenuation, dispersion and backscatter thus encode volumetric information of grain size and shape. On the contrary, inversion of these scattering behaviours determines the grain size and shape. The purpose of this study is to characterize polycrystalline grain size and shape by making full use of the linkage between microstructure and ultrasound attenuation, dispersion and backscatter.