Laser Optoacoustic Method for Quantitative Estimation of Porosity in Cast Dispersion-Strengthened Metal-Matrix Composite Materials

Abstract

A laser optoacoustic method for quantitative assessment of the volumetric porosity of cast dispersion-strengthened metal-matrix composite materials has been proposed and experimentally implemented. The method is based on a statistical analysis of the distribution of amplitudes of backscattered broadband pulses of longitudinal acoustic waves in the tested materials. Laser excitation and piezoelectric recording of ultrasound is implemented with one-way access to the test object using a special laser-ultrasonic transducer. Silumin-based composites reinforced with silicon carbide microparticles in various volume concentrations (0.033–0.135) and composites obtained by reaction injection moulding based on aluminum reinforced with intermetallic $${\text{A}}{{{\text{l}}}_{3}}{\text{Ti}}$$ (volume concentration 0.04–0.115) have been studied. For both types of composites, the distribution of amplitudes of backscattered ultrasonic signals is approximated by a Gaussian distribution function applicable for a large number of statistically independent quantities. The empirically obtained dependence of the half-width of this distribution on the volumetric porosity of composites of two different types is approximated by the same linear function regardless of the manufacturing technology, as well as of the type, size, and concentration of strengthening particles.