Research on Nondestructive Material Characterization with Multi-function Acoustic Microscope System

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A multi-function acoustic microscope system combined three system functions of imaging by point-focus-beam (PFB), quantitative measurement by line-focus-beam (LFB) and directional PFB microscope system with two functions of imaging and quantitative measurements has been developed as a new research tool for material characterization.To confirm the imaging perfomance with complex signals, imaging for fused quartz plates formed topographic lattice patterns were made with both amplitude and phase modes. Contrasts of topographic shapes on the specimen surface have been analyzed quantitatively by measuring amplitude and phase images simultaneously.In imaging of LiTaO_3 wafer with partially domain-inverted regions, contrast was observed at domain boundary in spite of same elastic properties. It has been showed that such contrast was caused by reflecting leaky surface acoustic wave (LSAW) due to difference of electrical properties at the domain boundary.The directional PFB acoustic device was applied for imaging of an MgO crystal with vertical cracks on the surface. The spaces of fringes produced in parallel to cracks were different in propagation directions of LSAWs.It has been proved that LSAW velocity of each direction could be characterized quantitatively.The system has been demonstrated for investigation of polycrystalline samples of pure Ti and Mn-Zn ferrite with average grain size of 100μm. Directional acoustic images were obtained at 225 MHz for several different propagation derections of LSAWs. Anisotropy measurements of LSAW velocity in some grains of the samples have been perfomed through V(z) curve analysis.Anisotropic elastic properties of each grain have been characterized both in imaging and quantitative measurements.