Fracture surface analysis of AA2218 Al-alloy MMCs and squeeze pressure effect on fracture mechanism

Abstract

A novel stir casting technique have been used for the development of AA2218-based metal matrix composite with the reinforcement of Al2O3 (TiO2) particles. Coarser Al2O3 and finer TiO2 particles are ball milled together after mixing in different proportion to achieve coating of the coarser particles by the finer one to promote wettability. The composite have been prepared by the addition of ball milled powder by 2% and 5% weight fraction in an aluminium melt. The developed as cast composites have been artificially aged using T61 heat treatment at 510°C for 4 hours and peak aging at 170°C for 10 h followed by squeeze cast between 100–220 MPa pressure. Tensile studies have been conducted on the specimens. Hardness and tensile strength is increased by adding alumina and TiO2. The improvement in ductility has been observed after aging at higher squeeze pressure. The fractured surfaces of tensile test specimens have been analysed and mechanism of fracture along with the effect of squeeze pressure and effect of particle wt% has been discussed.