Plasticity and ductility of an anisotropic recrystallized AA2198 Al-Cu-Li alloy in T3 and T8 conditions during proportional and non-proportional loading paths: simulations and experiments

Xiang Kong (1) , Jianqiang Chen (1) , Yazid Madi (1) , Djamel Missoum-Benziane (1) , Jacques Besson (1) , Thilo F. Morgeneyer (1)

1 CDM - Centre des Matériaux

The anisotropic material behaviour of a recrystallized AA2198 Al-Cu-Li alloy in T3 and T8 conditions was assessed by proportional loading of uniaxial-tension specimens in rolling (L), transverse (T) and diagonal (D) orientations. The width and longitudinal strains were measured to quantify plastic anisotropy. Notched-tension samples were tested in L and T directions. The material showed weak anisotropy in terms of stress strain curves and a moderate plastic anisotropy, consistent with its texture obtained by EBSD. An anisotropic Bron-Besson type material model was identified using this data base and a micro shear-only (SO) test. The model succeeded in predicting the behaviour of micro specimens for proportional tension-only (TO) loading and non-proportional load path changes including 'shear to tension' (ST) as well as 'tension to shear' (TS) tests. The non-proportional loading was achieved using a newly designed cross shaped sample. It was loaded in one direction, unloaded and subsequently loaded in the orthogonal direction till fracture. The average stretch to fracture of both alloys measured by a four point frame optical extensometer decreased by 29% and 16% for T3 and T8 respectively for the 'shear to tension' experiment compared to the proportional TO experiment. This reduction was suspected to be linked to either damage development under shear and/or high stress levels during tension due to the hardening of the material during shear. The average stretch to fracture of 'tension to shear' tests was reduced by 10% for 2198T3 and hardly reduced for 2198T8 compared to the stretch to fracture of the SO tests. However, the results exhibited a strong scatter for both heat treatments. The ductility scatter was attributed to necking and damage development in tension that can affect strain localization, associated fracture path and ductility, as observed by DIC and fractography.

Mots clés: Al-Cu-Li alloy; plastic anisotropy; characterization; non-proportional load path change; ductile fracture

Domaines: Matériaux; Génie mécanique [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]; Mécanique des structures [physics.class-ph]

Xiang Kong, Jianqiang Chen, Yazid Madi, Djamel Missoum-Benziane, Jacques Besson, et al.. Plasticity and ductility of an anisotropic recrystallized AA2198 Al-Cu-Li alloy in T3 and T8 conditions during proportional and non-proportional loading paths: simulations and experiments. 2022. ⟨hal-03497233v2⟩