Fracture behaviour of an Al-Mg-Si industrial alloy

The tensile fracture behaviour of an Al-0.89 wt.% Mg2Si industrial alloy is studied. It is found that the alloy deforms in a highly localised way only in the underaged (UA) state. In the peak aged (PA) condition the hardening precipitates are often by-passed by an Orowan mechanism, which predominate s in the overaged (OA) state. in the UA condition, the stress concentration is shown to be large enough to nucleate cracks at the particle interfaces provided the sheer strain has reached the critical value for cutting the pr ecipitates into pieces. In the PA and OA conditions, failure results from c oalescence of voids nucleated at large AlFeSi and smaller (Mg + Si) particl es. It is shown that none of these particles are responsible alone for frac ture. In contrast. ductility and rupture surfaces are consistent with a dam age mechanism whose nucleation step is the coalescence of voids nucleated a t large AlFeSi and neighbouring (Mg + Si) particles. (C) 2001 Elsevier Scie nce B.V. All rights reserved.