Rapid detection of inclusion particles in recycled aluminum materials by laser-induced plasma optical emission spectrometry with scanning laser beam

This paper describes an analytical method to evaluate the kind and the number of inclusion particles on the surface of a recycled Al ingot using laser-induced breakdown spectrometry (LIBS) with scanning laser beam. The surface was observed with scanning electron microscope - energy dispersive X-ray spectrometry (SEM-EDX) as well as scanning LIBS in the same viewing positions, in which inclusion particles of Si and Fe compounds were found. By measuring the emission intensity of the Fe I 358.119-nm and Si I 288.160-nm lines, the lateral distribution of Si and Fe inclusion particles was estimated from 2D intensity maps of these emission lines. The lateral resolution of the scanning LIBS was about 100 μm, which was restricted by the size of an ablated crater and the surrounding area; therefore, it is difficult to evaluate the actual number of fine inclusion particles (one or more particles may be counted to be a single particle). Nevertheless, the scanning LIBS has an advantage that the analysis can be conducted easily and rapidly compared to conventional analytical methods for inclusions. In our LIBS apparatus, the analysis for a sample surface of 4.0 × 5.0 mm2 was finished in about 40 min. and the time would be reduced if the spectrum analysis is automated on a computer. Accordingly, it is expected that the scanning LIBS can be utilized to consult on the quality of recycled Al materials in the recycling sites.