Effects of Pre-Stretching on Creep Behavior, Mechanical Property and Microstructure in Creep Aging of Al-Cu-Li Alloy

• Main Authors: Jin Zhang, Zhen Jiang, Fushun Xu, Mingan Chen
• Format: Article
• Language: English
• Published: MDPI AG 2019-01-01
• Series: Materials
• Subjects: Al-Cu-Li alloy; creep aging; pre-stretching; microstructure; mechanical property
• Online Access: https://www.mdpi.com/1996-1944/12/3/333

The effects of pre-stretching on creep behavior, mechanical properties and microstructure during the creep aging process of Al-Cu-Li alloy were investigated. AA2195 was taken as the representative of Al-Cu-Li alloys. It is found that the total creep strain and strength property of creep aged AA2195 specimens can be improved through effective pre-stretching. Unlike with artificial aging, yield strength increased increasing by 47%. The TEM images show that the constitution of aging precipitates in the creep-aged specimens are obviously changed by pre-stretching. Precipitates in the 2% pre-stretched specimen are mainly composed of T₁ phase, while a great amount of θ’ phase accompanied with a few T₁ phase were found in the non-pre-stretched specimen. Moreover, pre-stretching introduces many dislocations which benefit the creep deformation, but the increasing dislocation density also accelerates the nucleation and growth of the precipitates as well. The premature T₁ phase has a great blocking effect to the dislocation motion, creating a lower decrease rate but a longer duration in the early creep stage. Except for the initial dislocations, the dislocation motion in the creep aging process is also a favorable factor to precipitate the T₁ phase.