Ο ρόλος του διαχωρισμού και κατακρημνισμάτων στους μηχανισμούς διεπιφανειακής ενίσχυσης κράματος αλουμινίου ενισχυμένου με SiC όταν υπόκειται σε θερμομηχανική κατεργασία

Abstract

Metal Matrix ceramic-reinforced composites are rapidly becoming strong candidates as structural materials for many high temperatures and aerospace applications. Metal matrix composites combine the ductile properties of the matrix with a brittle phase of the reinforcement, leading to high stiffness and strength with a reduction in structural weight. The main objective of using a metal matrix composite system is to increase service temperature or specific mechanical properties of structural components by replacing existing superalloys. The satisfactory performance of metal matrix composites depends critically on their integrity, the heart of which is the quality of the matrix-reinforcement interface. The nature of the interface depends on the processing of the metal matrix composite component. At the micro-level the development of local stress concentration gradients around the ceramic reinforcement, as the metal matrix attempts to deform during processing, can be very different to the nominal conditions and play a crucial role in important microstructural events such as segregation and precipitation at the matrixreinforcement interface. These events dominate the cohesive strength and subsequent mechanical properties of the interface. At present the relationship between the strength properties of metal matrix composites and the details of the thermo mechanical forming processes is not well understood. The purpose of the study will is to investigate several strengthening mechanisms and the effect of thermo-mechanical processing of SiC particulate reinforced A359 aluminium alloy composites on the particle-matrix interface and the overall mechanical properties of the material. From experiments performed on composite materials subjected to various thermo-mechanical conditions and by observation using SEM microanalysis and mechanical testing, data were obtained, summarised and mathematically/statistically analysed upon their significance. An analytical model to predict the interfacial fracture strength in the presence of material segregation was also developed during this research effort. Its validity was determined based on the data gathered from the experiments.