In-situ formation of composite having hard outer layer based on aluminum dross reinforced by SiC and TiO2

Abstract

In-situ formed two-layer composite was prepared from aluminum dross reinforced with various percentages of SiC and TiO2. Nano powder mixtures were prepared by mechanical alloying. X-ray diffraction (XRD) and transmission electron microscopy were utilized to evaluate the milled powders. The powders were cold pressed under 20 MPa and sintered for 1 h at 1500 °C. The sintered samples were investigated by XRD and scan electron microscopy. Bulk density and apparent porosity were also determined by liquid displacement method. The microhardness, fracture toughness, elastic moduli and electrical conductivity were also studied. The results revealed that a significant reduction in crystallite size was occurred after milling the powder. After sintering, two-layer composite was in-situ formed. The reinforcements were homogenously distributed in the matrix with formation of new phase as TiC. The bulk density was increased while the apparent porosity was decreased with increasing the reinforcement's content. Furthermore, mechanical properties of outer layer were enhanced with increasing the amount of reinforcements; its hardness was higher than that of the inner layer. The electrical conductivity of whole-bulk composite was also increased with increasing the reinforcement percentage.