Mechanical behaviour of the interphase between matrix and reinforcement of Al 2014 matrix composites reinforced with (Ni3Al)(p)

The 2XXX series aluminium alloys reinforced with intermetallics present a special behaviour due to the reaction between matrix and reinforcement. This reaction forms an interphase that influences the mechanical and chemical behaviour of the composite, reducing the capability of the material to improve its properties after heat treatment. In this work, an approach is made to the study of this interphase, using particulate intermetallics with the same chemical and stoichiometric composition but obtained in different ways: mechanical alloying and gas atomising. A micro structural study was carried out by SEM, including qualitative analysis, showing the chemical gradient formed at the interphase both as-extruded and after T6 treatment. The mechanical behaviour of the interphase is studied through nanoindentation that allows the determination of hardness and Young modulus. Finally, all these properties are correlated with a fractrographic study of the fracture mechanisms. A harder interphase is formed for the mechanically alloyed system promoting a transgranular cleavage fracture micromechanisms, while intergranular cleavage fracture is found in atomised intermetallic containing composites. (C) 2002 Elsevier Science Ltd. All rights reserved.