The mechanical and physical properties of Metal Matrix Composite (MMC) are very susceptible to the distribution of dispersed particles. At present, only the content of dispersed particles is measured with a gravimetric analysis. However, this measurement is a type of destructive method and requires much time for the chemical analysis. Accordingly, the development of a nondestructive method to simply evaluate the dispersed particles becomes an important subject for the quality insurance of MMC. Aiming at a development of a nondestructive method to inspect microscopic particles in the interior of MMC, we investigated the propagation of ultrasonic waves in aluminium alloy composite (Al/SiCp). Providing some samples of Al/SiCp with different SiCp contents and different SiCp sizes, we examined the effects of both volume fraction and size of SiCp on ultrasonic propagation characteristics. As an incident ultrasonic wave, a short pulse signal of a high frequency (100 MHz) was used. The detected signals propagating through the samples were passed to a computer for waveform analysis. Resulting from the experiment and analysis, the following important laws of ultrasonic waves were revealed.
- the propagation time decreases with the increase in volume fraction of SiC particles;
- the pulse width of the propagated signals becomes wider with the increase in SiCp sizes.
We studied this phenomenon theoretically with a probabilistic new idea, and derived the formulas for the relationship between ultrasonic characteristics (velocity and waveform) and SiCp distributions (volume fraction and size). This new finding enables us to nondestructively evaluate both volume fractions and mean sizes of microscopic particles in MMC.
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