Investigation of tensile and compressive creep behaviour of AA2050-T34 during creep age forming process

The tensile and compressive creep behaviour of aluminium alloy 2050 with T34 initial temper (AA2050-T34) during creep-Ageing process has been experimentally investigated and analysed in detail. Both tensile and compressive creep-Ageing tests under various stress levels (ranging from 100 MPa to 187.5 MPa) have been carried out at a temperature of 155 °C for 18 hours. The results show that creep strains under tensile stresses are much larger than those under the same levels of compressive stresses and a new "double primary creep feature" with five-stage creep behaviour has been observed in the alloy during the creep-Ageing tests. The conventional power-law creep equation was applied to analyse the new creep behaviour of the alloy at the steady-state creep stage. Furthermore, the power-law relationship between the applied stress and the corresponding creep strain rate was found to be effective in all creep-Ageing stages of the alloy and was used for further analysis. These analyses indicate that the dislocation and diffusion mechanisms may both contribute to this new creep behaviour and may play different roles in different creep-Ageing stages. Moreover, the evolution of the creep resistance or threshold creep stress of the alloy during the creep-Ageing process was quantitatively investigated by the proposed relationship. These results help to not only understand the new creep behaviour of AA2050-T34 during the creep-Ageing process, but also facilitate further constitutive modelling of this new creep behaviour for its creep age forming applications.