Effect of processing parameters on physical properties of spray formed and stir cast Al-2Mg-TiO2 composites

In the present study, a modified spray forming set-up has been used to prepare Al-2Mg-TiO, composites. Up to 6 and 11% by weight of the rutile particles have been successfully incorporated in A1-2Mg matrix using the modified spray forming technique. The density measurement reveals that the optimum nozzle-to-substrate distance is 30 cm and the optimum speed of rotation of the substrate is 8 rpm. The electrical resistivity measurement shows that resistivities of composites are marginally greater than the base alloy. The cold rolled alloy shows a wider hump in the resistivity variation, due to the recrystallization of the matrix. Similar observations are made in case of both stir cast and spray formed A1-2Mg-TiO2 composites. The kinetics of recrystallization of composites is faster than the matrix alloy. This is evident from relatively small hump in resistivity variation with temperature of composites. The fast recrystallization kinetics in composites is due to the generation of dislocations owing to the thermal mismatch between the Al matrix and the rutile particles. In addition to the hump at lower temperature, resistivity measurement of A1-2Mg-TiO2 composites shows a peak at temperature between 350 and 400degreesC. The peak is due to the formation of the TiAl3 phase at TiO2 particle-matrix interface. Thermal conductivity of spray formed Al-2Mg-TiO, composite is greater than the base alloy. (C) 2004 Elsevier B.V. All rights reserved.