EVALUATION OF AL-CU-MG-AG ALLOYS CONTAINING DISCONTINUOUS ALUMINA FIBERS .1. MICROSTRUCTURAL EVOLUTION

Composites were fabricated by infiltrating discontinuous alumina fibre (Saffil) preforms (V-f = 0.08 and 0.25) with Al-Cu-Mg-Ag alloys at tw o different magnesium levels. lit each composite, the preform binder, an aluminosilicate, reacted with the matrix magnesium to form MgO and alumina. Some magnesium was also absorbed by the fibres, although in t his case no second phase was produced. Upon solution treatment, furthe r reaction occurred such that only one of the composites was left with any magnesium in its matrix. In this composite, artificial ageing pro duced Omega phase precipitate, to give a hardening response closely si milar to that in the corresponding unreinforced alloy. In the other co mposites, theta' phase was formed and this resulted in less effective matrix hardening. (C) 1996 Elsevier Science Limited