Analysis, representation, and prediction of creep transients in Class I alloys

Solute-drag (SD) creep in Class I alloys is characterized by several features. Among these is the presence of “inverse” creep transients, which are unique to these solid-solution alloys and the SD creep mechanism. Creep transients in commercial AA5083 materials under SD creep are analyzed using a model based on a graphical construct previously proposed. It is observed that transient behavior can be represented in a general fashion which predicts the decay in relative transient size as a function of strain. Experimental data for SD creep are presented using the proposed graphical construct to determine the dependence of dislocation glide speed on stress and the dependence of equilibrium mobile dislocation density on stress. It is observed that the high stress exponents of the commercial AA5083 materials under SD creep, relative to low-impurity, binary Al–Mg materials, are primarily the result of an increased dependence of dislocation glide speed on stress.