The θ projection method applied to small strain creep of commercial aluminium alloy

Abstract

The paper describes the early uniaxial creep behaviour of an airframe aluminium alloy (2419-T851). Tests were conducted over the temperature range 373 to 463 K and for rupture lives up to 7000 ks. The shapes of creep curves were fitted using either the conventional 4-Θ equation or the recently proposed 6-θ equation. Coefficients allowing the interpolation of times to small strains were produced and the accuracy of such interpolations was checked against experimental values. At small strains, the 4-Θ equation produced systematic errors but the 6-θ function gave expected values of errors which could not be distinguished from zero. At larger strains, both methods yielded zero mean errors. The procedures are discussed in terms of the likely deformation mechanisms which might lead to the observed forms of the projection equations. It seems likely that very early creep contains some strain due to anelastic grain boundary relaxation.