Microstructural and mechanical behavior of bimodal reinforced Al-based composites produced by spark plasma sintering and FSP

Spark plasma sintering (SPS) is a powder metallurgy technique where uniaxial force and pulsed direct current are employed to perform metallic or ceramic particle consolidation in very short times. The high heating and cooling rates allow to prevent excessive grain growth favoring densification. Spark plasma sintering has been recognized, in the recent past, as a very useful method to produce metal matrix composites characterized by enhanced mechanical and wear properties. Obviously, the materials final properties are strongly related to the reinforcement types and percentages as well as to the processing parameters employed during synthesis. The present paper analyses the effect of microscopic and nanometric alumina particles, blended to pure aluminum in different combinations, on the final properties of metal matrix composites produced via SPS. The SPSed composites were friction stir processed (FSPed), and the processing forces and the heat input in the materials were analyzed. The microstructural and mechanical behavior of the processed materials are shown to be strongly dependent on the starting material properties and on the processing parameters employed during FSP.