High temperature cleavage fracture in 5383 aluminum alloy

The fracture behavior of the 5383 aluminum alloy is investigated at high temperature (490–560 °C) and high strain rate (l0−2–25 s−1) by the secondary tensile test. A dramatic decrease of ductility is observed at all temperatures for the highest strain rates. The fracture surfaces show a mixture of cleavage facets and smooth intergranular regions. Cleavage facets have been clearly identified by their planar, intragranular character and their river patterns. Two types of cleavage facets are present in approximately equal proportions, {100} and {110}. A maximum of area fraction of cleavage is observed both as a function of temperature and strain rate. The experimental observations suggest that the apparition of cleavage is related to liquid metal embrittlement (LME) in the first stages of deformation, which enables the formation of extremely sharp cracks. These cracks are able to initiate cleavage fracture possibly because of high temperature inhibition of plasticity due to an increase of Stacking Fault Energy close to the melting point.