Effect of processing parameters on physical properties of spray formed and stir cast Al-2Mg-TiO_2 composites

摘要

In the present study, a modified spray forming set-up has been used to prepare Al-2Mg-TiO_2 composites. Up to 6 and 11 percent by weight of the rutile particles have been successfully incorporated in Al-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 Al-2Mg-TiO_2 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 Al-2Mg-TiO_2 composites shows a peak at temperature between 350 and 400 deg C. The peak is due to the formation of the TiAl_3 phase at TiO_2 particle-matrix interface. Thermal conductivity of spray formed Al-2Mg-TiO_2 composite is greater than the base alloy.