On two types of creep behaviour of F.C.C. solid solution alloys

Abstract

On the basis of careful steady state creep rate measurements in a broad stress interval at 623 K the “critical”' stress σc is determined at which the transition from the behaviour characteristic for Class I to that characteristic for Class II solids (according to Sherby's and Burke's classification) takes place in an Al–5.5 at% Mg solid solution alloys. The critical stress σc is then used to determine the boundary of the regions of the conditions at which solid solution alloys behave as Class I and Class II solids, respectively. It is taken into account that, generally, Dc ≠ Dg (Dc and Dg are the coefficients of diffusion that controls dislocation climb and dislocation glide, respectively). For this determination the Mohamed-Langdon criterion is applied. The prediction is made of creep behaviour of several binary solid solution alloys and is found in agreement with the experiment. Also the investigation of transient creep (primary creep and the creep taking place after stress changes in the secondary as well as in the primary creep stage) gives evidence of two types of creep behaviour of an Al–5.5 at% Mg solid solution alloy. [Russian Text Ignored]