Purifying effects and mechanism of a new composite filter

A new composite filter was obtained by dipping a ceramic foam filter (CFF) into a molten flux (JDN-I flux). Results indicated that without filtration, the microstructure of A356 scrap contained many Al2O3 inclusions which were reunited and whose size was increased from 6.0 μm to above 20.0 μm. However, after being filtered with composite filter, no obvious inclusions above 6.0 μm could be found in the microstructure. The tensile strength and the elongation of the samples purified with the composite filter increased by 19.2% and 116.7%, respectively, compared with those without filter, and then, the same properties purified with the common filter only increased by 13.2% and 50%, respectively. The flux layer existed only in the filter. Micro-size inclusions below 10 μm were agglomerated on the inner wall and could be removed efficiently. The difference in purifying mechanism between the new composite filter and general CFF was also discussed.