Microestructural Characterization of Predeformed Al-Cu Based Alloys Microalloyed with Si-Ge.

M.V. CASTRO RIGLOS; A. TOLLEY

Merida

Congreso; 11o Congreso Interamericano de Microscopía (CIASEM 2011); 2011

CIASEM

Age hardenable aluminium alloys modify their mechanical properties in accordance to the ageing heat treatment applied to them. Adequate hardness values can be achieved for specific applications by carefully tailoring the microstructure. Al-Cu system is one of the most widely studied of the “age hardenable” type. In this system, hardness is mainly enhanced by the presence of θ’’ intermediate phase, but also, some precipitates from θ’ phase might contribute [1]. One method that can be useful for modifying hardness evolution is to add microalloying elements. Si and Ge additions have proved to be very effective in this sense by generating Si-Ge precipitates that provide heterogeneous nucleation sites [2]. Another method is to apply a plastic deformation, previous to the ageing heat treatments, and so introducing dislocations that can serve as heterogeneous nucleation sites as well as favouring the solute diffusion during subsequent heat treatments. For example, it was observed in Al-Cu deformed (by lamination) at room temperature a stimulated appearance of θ’ phase [3]. The aim of this work was to analyze the combined effect of deformation (previous to the ageing treatment) and Si-Ge microalloying in Al-2at.%Cu on the hardening response during artificial aging, and the formation of secondary phases. Heat treatments were performed at 160°C. The hardness evolution during aging was studied by Vickers microharndess measurements with a Mitutoyo Hardness Testing machine, using a weight of 100g. The microstructural evolution was studied by means of transmission electron microscopy (TEM) techniques in a Philips CM200 microscope.