SPECIATION OF INCLUSIONS IN ALUMINUM BY X -RAY-DIFFRACTION AND FLUORESCENCE METHODS COMBINED WITH PRECONCENTRATION BY FILTRATION AND SELECTIVE DISSOLUTION

A method for the determination of trace amounts of corundum (alpha-Al2 O3), alpha-quartz and other metallic elements as inclusions in alumini um with X-ray diffraction and fluorescence analyses has been developed . An aluminium sample was melted and filtrated through a porous alumin a filter (100 mu m in pore size). These inclusions were concentrated i n a layer on the filter with almost 100% recovery, and collected on a membrane filter after dissolving matrix metallic aluminum with a bromi ne-methanol solution. The X-ray intensities of the inclusions on the m embrane filter could be measured without any significant interference of the coexisting materials, except for light elements in relatively. large amounts of inclusions. The regression coefficients between the i ntensities and amounts of standard specimens were 0.990 similar to 0.9 99 and the reproducibilities were satisfactory. Corundum in the range of 0.07 similar to 0.5 ppm and alpha-quartz in the range of 0.02 simil ar to 0.09 ppm and the other metallic elements, such as Mg, Al, Si, Ti , Mn, Fe and Cu at the ppb level were determined. Spinel and other inc lusions could also be determined by this method.