Influence of quench rate and microstructure on bendability of AA6016 aluminium alloys

Philippe Castany (1) , Frédéric Diologent (1) , Andreas Rossoll (1) , Jean-François Despois (2) , Cyrille Bezençon (2) , Andreas Mortensen (1)

1 EPFL - Ecole Polytechnique Fédérale de Lausanne
2 Novelis Switzerland SA

The influence of the quench rate after solution treatment on the bendability of AA6016 aluminium alloy sheets was investigated. Crack initiation during bending tests is found to be independent of quench rate whereas crack propagation is decreased after rapid quenching. A quantitative analysis of microstructures was carried out by transmission electron microscopy, focusing on grain boundary precipitates to correlate bending properties with microstructure. Crack initiation occurs by voiding at large micron-size intermetallic AlFeSi particles in shear bands, as previously proposed in the literature. Rapid quenching promotes the formation along grain boundaries of spherical Mg2Si precipitates to the detriment of elongated Si precipitates that dominate after slow cooling. These Si grain boundary precipitates affect micro-voiding processes that drive crack propagation, which explains the observed dependence of the extent of cracking on quench rate. The grain boundary precipitate density has on the other hand no effect on crack initiation or propagation.

Mots clés: Aluminum alloy; Bendability; Microstructure; Grain boundary precipitates; Transmission electron microscopy

Domaines: Matériaux

Philippe Castany, Frédéric Diologent, Andreas Rossoll, Jean-François Despois, Cyrille Bezençon, et al.. Influence of quench rate and microstructure on bendability of AA6016 aluminium alloys. Materials Science and Engineering: A, 2013, 559, pp.558-565. ⟨10.1016/j.msea.2012.08.141⟩. ⟨hal-00763170⟩