Heat treatable aluminum based metal matrix nanocomposites

Metal matrix nanocomposites (MMnCs) based on Al2618 aluminum alloy and reinforced by oxide fragments produced in-situ and/or SiC nanoparticles added ex-situ were prepared via different powder metallurgy routes. High-energy ball milling was performed in order to deform powders, reduce grain size, disperse ex-situ reinforcement and produce in-situ nanometric oxide fragments. Hot extrusion and hot rolling allowed to sinter powders, while cold rolling was used as final forming process. Ageing behaviour of MMnCs was extensively studied, also from a kinetic point of view, and influence of reinforcement was assessed. Nanocomposites exhibited reduced response to age hardening, accelerated kinetics and hindering of GP zone formation. Microstructure of rolled samples was characterized by TEM analysis. Mechanical behaviour was analyzed in different heat treatment conditions and at different temperatures; the role of reinforcement in retaining Portevin – Le Chatelier effect after ageing was studied. MMnCs showed improved performances in terms of tensile strength.