Creep of high-purity aluminum

Abstract

A study was made of cold-drawn alumin um at 105° F, to determine t he effects of vari at ions of creep rate on t he mecha nism of deformation. Strai n-hardening was found to decrease monotonically with increase in strain during first stage of creep . The extension on loading and the extension at t he begin ning of t he t hird stage both increased wit h incr ease in stress. Cyclic temperature changes appeared to in crease t he duct ility. Discontinuous flow was evidenced in constant-load creep tests at 105° F a nd in te nsile tests co nducted at 80° F. Conformance to Andrade's law of transien t fiow was found within a limited r a nge of strain rates. Sigmoidal curves were produced t hat depicted t he relationship between stress and creep rate. A mechanism of fiow based on obser ved structural ch anges is proposed.