Anisotropy effect on the creep properties of a Al-Cu-Si-Mg alloy: from 1D specimen tests to material modelling and its experimental validation
Elisabetta Gariboldi
Departimento di Meccanica, Politecnico di Milano
10:30 - 11:20 Monday 28 September 2015 Hörsaal I, Alte Technik The mechanical properties of aluminium alloy forgings are widely affected by the extent and direction of plastic flow as well as by their heat treatment. Further, when service conditions combine high temperature and mechanical loading, creep phenomena are involved and anisotropy of creep behaviour is expected. Further, in parts of complex geometry stress redistribution and localized creep damage takes place, both affected by the microstructural features.
The present research work is focused on the effect of microstructure anisotropy on the creep properties of an Al-Cu-Mg-Si alloy. A first step was performing 1D creep tests in the temperature range 130-170°C on conventional specimens sampled in different orientation from an axisymmetric forged component. Results confirmed effect of sampling direction either on the progressive accumulation of creep strain and on the rupture times. A simple constitutive model of mechanical behaviour was set up taking into account the material anisotropic by means of phase mixture model as well as the overaging processes of the age-hardening alloy matrix. It was then applied to predict the creep behavior and stress-redistribution on specifically designed flat notched specimens, representative of complex-shape materials. The model was validated by interrupted experimental creep tests on these specimens where macroscopic strain field was measured by Direct Image Correlation method. The final modelled strain and stress distributions of notched specimen were combined to SEM microstructural investigations in order to properly include damage effects in the model.
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Institute of Solid State Physics
