Creep ageing behaviour assisted by electropulsing under different stresses for Al-Cu-Li alloy
(1. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China;
2. State Key Laboratory of High-Performance Complex Manufacturing, Central South University, Changsha 410083, China;
3. Light Alloys Research Institute, Central South University, Changsha 410083, China)
2. State Key Laboratory of High-Performance Complex Manufacturing, Central South University, Changsha 410083, China;
3. Light Alloys Research Institute, Central South University, Changsha 410083, China)
Abstract: The influence of electropulsing on the creep behaviour, strength, and microstructure of an Al-Cu-Li alloy during creep ageing was investigated. Electropulsing assisted creep ageing (ECA) and conventional creep ageing (CCA) were carried out under various stress levels and time conditions. Applying electropulsing results in a noteworthy change of creep behaviour, including a variation in creep curves, an increased creep rate in early stage, and an improved creep strain. The ECA specimen experiences a shorter time to the peak strength, and an increase in elongation by ~17.4% without loss of the peak-aged strength compared with CCA specimen. The ultrafine nano-size subgrains are observed to form under electropulsing, which can result in an increased creep strain by increasing grain-boundary sliding. The enhancement of both dislocation interactions and solute diffusion under electropulsing is considered as a primary cause of disappearance of a platform stage during early creep ageing. Some of T1 precipitates around the grain boundary are observed in the peak ECA sample, resulting in an occurrence of transgranular fracture, which is further responsible for an increased elongation of the ECA specimen.
Key words: Al-Cu-Li alloy; creep ageing; electropulsing; precipitation; microstructure