Study on hot deformation behavior and workability of stir-cast Al6063-6wt.% steel_pbased composites

Investigation on the hot deformability and workability of stir cast 6 wt.% steel particles reinforced aluminium 6063 matrix composites was undertaken in this study. Flow stress - strain curves generated from hot compression tests performed at strain rates of 0.01, 0.1, 1, and 10 s-1, and temperatures between 200-400°C, were used to study the flow behavior of the composite, while processing map developed from analyses of the deformation data, was used to establish the deformation mechanisms and processing safe zones for effective workability. Flow stress oscillations were observed to be prevalent at lower deformation temperatures and strain rates; largely due to the settling of reinforcement particles at grain boundary vicinities, rather than a homogeneous distribution. Also, the flow behaviour was largely strain rate insensitive. The dominant flow mechanism based on the flow stress patterns, processing map and microstructural validation was established to be dynamic recovery. Safe regions for processing based on Murty's and Gegel's criteria established the safe processing zones to be ~270-400°C at 0.01-1.0 s-1 and 380-400°C at 10 s-1. Deformation processing was unsafe at 200-260°C at 0.01-1.0 s-1 and between 200-380°C at 1.0-10 s-1.