Stress-level dependency of creep ageing behavior for friction stir welded Al-Cu alloy

• Published in: Journal of Central South University Vol. 29; no. 9; pp. 3030 - 3053
• Main Authors: Wang, Dong-yao, Zhan, Li-hua, Zhong, Jue, Tang, Zhi-mao, Zeng, Quan-qing, Gan, Ke-fu
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01.09.2022; Springer Nature B.V
• Subjects: Aerospace engineering; Aging; Aging (metallurgy); Aluminum base alloys; Copper; Creep strength; Dislocation density; Engineering; Friction; Friction stir welding; Grain size; Metal plates; Metallic Materials; Microstructure; Strain rate; Stress; Tensile properties; Welded joints; precipitation microstructure evolution; 析出相演变; 力学性能; inhomogeneous gradient microstructure; thick Al-Cu alloy plate; 铝铜合金厚板; friction stir welding; 搅拌摩擦焊; creep age forming; 蠕变时效成形; mechanical property; 不均匀梯度组织
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-022-5139-x

Creep ageing forming (CAF) has been widely used in the aerospace engineering, but how to optimize the processing conditions, especially under complex stress state of the CAF process for large-size components produced by friction-stir welding is still a great challenge to now. In this work, the creep ageing behaviors and underlying microstructure evolution of a thick friction-stir welded Al-Cu alloy plate after CAF process under different stress levels are systematically investigated. The creep strain and the strength of the joint are both significantly increased when the stress is close to the average yield strength of the initial weld joint. The grain size reduces while the local strain and dislocation density increase from top to bottom of the NZ; hence, the bottom layer of the weld joint exhibits higher creep strain and steady-stage creep strain rate during the CAF process. The results reveal that the gradient microstructures sensitive to the stress level effectively govern the creep-ageing performance from the upper to the bottom layer in a thick friction stir welded Al-Cu alloy plate. Rationally increasing the initial dislocation density of the weld joint can both enhance the tensile properties and promote the creep deformation of the weld joint for CAF process.