Development and implementation of strategies for the incorporation of reinforcing elements in aluminium alloys by solid state processing

Dissertação para obtenção do Grau de Mestre em Engenharia Mecânica

This investigation aimed to study new surface processing strategies to produce reinforced surface metal matrix composites by Friction Stir Processing. The first consisted on pre-placing reinforcing particles over the surface, while the second used consumables drilled holes filled with reinforcing particles. Each strategy was investigated using an electric current in a process under patenting. Aluminium AA5083-H111 plates were used as base material. Silicon carbide and alumina particles with median sizes of 35 and 45 μm, respectively, were used. Pre deposition of reinforcing particles proved to be more effective than the use of consumable tools packed with particles. The last ones produced coatings with a non homogeneous distribution and poor bonding between the substrate and the reinforcing coating. The pre deposition of alumina produced a higher extension and depth of reinforced layer and an increase in hardness of 60%, while silicon carbide produced an increase in hardness of 300 %, though in a smaller extension and depth than alumina under the same processing conditions. Using the electric current a significant raise of 500% and 40% was observed in extension and depth respectively, but hardness decreased by 10 %.