An Investigation of Compressive Creep Aging Behavior of Al-Cu-Li Alloy Pre-Treated by Compressive Plastic Deformation and Artificial Aging

• Published in: Materials Vol. 16; no. 5; p. 2054
• Main Authors: Liu, Jinqiu, Guo, Fuqiang, Matsuda, Kenji, Wang, Tao, Zou, Yong
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 02.03.2023; MDPI
• Subjects: Aging; Aging (artificial); Al-Cu-Li alloy; Alloys; Aluminum alloys; Aluminum base alloys; Cold flow; compressive creep; Copper; Creep tests; Deformation; Deformation effects; Dimensional stability; Dislocation loops; Grain boundaries; KAM; Mechanical properties; Metal forming; Nucleation; Phases; Plastic deformation; pre-aging; pre-deformation; Predeformation; Specialty metals industry; Stacking faults; Thickness ratio; Al-Cu-Li alloy; pre-deformation; compressive creep; KAM; pre-aging
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16052054

In this paper, the effects of compressive pre-deformation and successive pre-artificial aging on the compressive creep aging behavior and microstructure evolution of the Al-Cu-Li alloy have been studied. Severe hot deformation mainly occurs near the grain boundaries during the compressive creep initially, which steadily extends to the grain interior. After that, the T phases will obtain a low radius-thickness ratio. The secondary T phases in pre-deformed samples usually only nucleate on dislocation loops or Shockley incomplete dislocations induced by movable dislocations during creep, which are especially prevalent in low plastic pre-deformation. For all pre-deformed and pre-aged samples, two precipitation situations exist. When pre-deformation is low (3% and 6%), solute atoms (Cu and Li) can be consumed prematurely during pre-aging at 200 °C, with dispersed coherent Li-rich clusters in the matrix. Then, the pre-aged samples with low pre-deformation no longer have the ability to form secondary T phases in large quantities during subsequent creep. When dislocation entangles seriously to some extent, a large quantity of stacking faults, together with a "Suzuki atmosphere" containing Cu and Li, can provide the nucleation sites for the secondary T phase, even when pre-aged at 200 °C. The sample, pre-deformed by 9% and pre-aged at 200 °C, displays excellent dimensional stability during compressive creep because of the mutual reinforcement of entangled dislocations and pre-formed secondary T phases. In order to decrease the total creep strain, increasing the pre-deformation level is more effective than pre-aging.