Transmitted light microscopy of a fibre reinforced metal

A method is presented for studying fibre damage in continuous fibre reinforced composites. It is based on contrasting the transmission of light through intact translucent fibres with the light through fractured or dead-ended fibres. The method is applied in order to detect processing-induced fibre fractures in aluminium reinforced with continuous alumina fibres

Structural phase transition in Al-Cu-Mg-Si alloys by transmission electron microscopy study on an Al-4wt% Cu-1 wt% alloy reinforced by SiC particles

The precipitation state of an Al-4 wt% Cu-1 wt% Mg-Ag alloy reinforced with SiC particles fabricated by squeeze casting is studied by transmission electron microscopy. As a consequence of an interfacial reaction the precipitation of the characteristic phases of the unreinforced alloy, Ω and S′, is suppressed and substituted by a new precipitation consisting of isolated nanoscaled rod-shaped precipitates and θ′ plates decorated with a further type of rod-shaped precipitates. These precipitates are the Q-Al5Cu2Mg8Si6 phase (hexagonal with a = 1.035 nm and c = 0.405 nm), and two other new phases also containing Al, Cu, Mg and Si, called QC (hexagonal with a = 0.670 nm) and QP (hexagonal with a = 0.393 nm). These three phases are based on the same latent lattice, the QP lattice. A phase transition model is proposed for these phases. It implies an ordering of the structures given by displacements of atoms from a lattice based on the common QP lattice. This approach is very promising for a better understanding of the precipitation in Al-Mg-Si-Cu alloys

Effect of SiO2 binder on the precipitation state of an AlCu4Mg1Ag/Saffil composite

The microstructure of an AlCu4Mg1Ag alloy reinforced with 15 vol% Al2O3-Saffil fibers was investigated by analytical transmission electron microscopy and compared to the microstructure of the unreinforced alloy. The investigation results show that the composite matrix is enriched in Si as a consequence of the interfacial reaction between the Mg from the alloy and the SiO2 from the fiber and fiber binder. The presence of Si in the composite matrix modifies the characteristic precipitation state of the monolithic Al-alloy: in the peak aged T6-temper, the phases Ω + S′ are substituted by a fine and homogeneous precipitation of θ′ plates, and a new type of rod-shaped precipitates. On overageing, these rod-shaped precipitates can be classified into two categories: precipitates containing Al, Cu, Mg, and Si (possibly a Q-phase precursor) and Si precipitates that act as nuclei for θ′

Behaviour of Al2O3-Al ceramic metal composites under projectile impact

The ballistic resistance of Al2O3-Al composites against 7.62 mm Armour Piercing projectiles was investigated. Edge-on Impact tests were conducted in order to characterise the fracture behaviour of the composites. Two material versions based on different Al2O3-preforms were tested. The ceramic preforms were infiltrated with a high-strength aluminium alloy by squeeze casting.L'objet de recherche est la résistance de composites de Al2O3 contre l'impact de projectiles perforants du calibre 7.62 mm. Des expériments du type 'Edge-on Impact' ont permis la charactérisation du comportement fragile de deux composites à base de Al2O3