Abstract: SiCp reinforced aluminium-matrix composites manufactured by using powder metallurgy method typically have inhomogeneity defects. To evaluate the inhomogeneity condition, conventional metallographic method would destroy the sample, and ultrasonic scanning method based on wave velocity has difficulties on defect locating and testing sensitivities. Collinear nonlinear ultrasonic method like harmonic generation is an optional solution, but the inhomogeneity induced nonlinearities are small and often masked under other sources of nonlinearities. To solve the aforementioned problems, a non-collinear nonlinear ultrasonic testing technique based on wave beam mixing is proposed to observe the nonlinearities of SiCp/Al samples, and the feasibility of the method to detect inhomogeneity defect is discussed. A non-collinear nonlinear ultrasonic system is developed to observe the wave beam mixing properties of LY12 Al alloy and SiCp/Al samples and the waveform mode transformation is obtained in the experiments, as well. The experimental nonlinearities have been successfully removed by spatial, mode, frequency and direction selection properties of the technique making the experimental method more robust. The experimental results show that the non-collinear technique based on wave beam mixing has the potential to be used to detect inhomogeneity defect of SiCp reinforced aluminium-matrix composites and the conclusion can be used in future scanning detection.

Key words: Aluminum-matrix composites, Beam mixing, Inhomogeneity, Non-collinear technique, Nonlinear ultrasonic