Deformation mechanisms in superplastic AA5083 materials
Article (1.111Mb)Abstract
The plastic deformation of seven 5083 commercial aluminum materials, produced from five different
alloy heats, are evaluated under conditions of interest for superplastic and quick-plastic forming.
Two mechanisms are shown to govern plastic deformation in AA5083 over the strain rates, strains,
and temperatures of interest for these forming technologies: grain-boundary-sliding (GBS) creep and
solute- drag (SD) creep. Quantitative analysis of stress transients following rate changes clearly
differentiates between GBS and SD creep and offers conclusive proof that SD creep dominates
deformation at fast strain rates and low temperature. Furthermore, stress transients following
strain-rate changes under SD creep are observed to decay exponentially with strain. A new graphical
construction is proposed for the analysis and prediction of creep transients. This construction
predicts the relative size of creep transients under SD creep from the relative size of changes in
an applied strain rate or stress. This construction reveals the relative size of creep transients
under SD creep to be independent of temperature; temperature dependence resides in the
“steady-state” creep behavior to which transients are related.
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