Evolution of the interfacial layer and its effect on mechanical properties in TiO2 nanoparticle reinforced aluminum matrix composites

Variations in the interfacial layer during annealing and their effects on the mechanical properties of titania nanoparticle-reinforced aluminium matrix composites were investigated. Three different types of reinforcing TiO2 particles (i.e., 15, 50, and 300 nm) were used and the composites were annealed at 500 C for up to 24 h. The small 15 nm particles, with high chemical potential energy, induced an enhanced decomposition process leading to the extension of the interfacial layer up to 12 h of annealing, in which Ti and O atoms were alloyed in the aluminium structure. The alloyed interfacial layer had beneficial effects on the mechanical properties of the aluminium-based composites in terms of their elastic modulus and yield stress. Furthermore, elongation to failure increased since the alloyed interfacial layer did not interfere with the movement of dislocations emitted at the interface of the particle, which continuously decomposed and shrank during annealing. Further annealing stimulated reduction processes, inducing the formation of alpha-Al2O3 and Al3Ti in the layer. When the particle size used was 300 nm, interfacial evolution behaviour was not observed at the interface due to the negligible decomposition behaviour of the particle under the annealing conditions.