Creep behaviour of icosahedral Al-Cu-Fe

Transient creep experiments have been performed on poly-quasicrystalline sp ecimens of the icosahedral Al-Cu-Fe phase. Three temperatures (870, 960 and 1000 K) have been selected in the ductile regime for creep stresses that r ange between 30 and 320 MPa. In these experiments, the specimens are first loaded in constant strain-rare conditions, then the testing machine is swit ched to load control and the specimens are allowed to deform under creep co nditions. One- or two-stage creep curves have been obtained depending on te mperature, stress and on the deformation level of the stress-strain curve a t which the creep tests were performed. When creep conditions are applied b efore the upper yield stress, at low stress, only a stage of continuous dec rease in creep rate is observed, while at higher stress this primary stage is followed by a stage of accelerated creep rate. These two-stage creep cur ves are predicted within the framework of the strain dependent friction str ess model. For creep tests beyond the upper yield stress, only the stage of accelerated creep rate is observed. No distinct steady-state stage has bee n observed for all investigated creep conditions. (C) 2000 Elsevier Science B.V. All rights reserved.