Microstructure and mechanical properties of self-reacting friction stir welded AA2219-T87 aluminium alloy

ABSTRACT

AA2219-T87 alloy was self-reacting friction stir welded at different traverse speeds. Joints produced at low traverse speed exhibit tunnel defects. The tunnel defects can be avoided by higher traverse speed, but excessive increase in traverse speed leads to the joint line remnants presenting in a linear geometry which comprises strength of the joint by providing an easier path for crack propagation. In the weld nugget zone, grains in the lower layer are coarser than those in the upper layer due to smaller extent of heat dissipation through the bottom shoulder. Extensive softening occurs in the weld zone owing to dissolution of the θ′ precipitates. Tensile strength of the defect-free joint reaches 74% of that of the base metal.

KEYWORDS:

• Self-reacting friction stir welding
• aluminium alloy
• microstructure evolution
• mechanical properties
• fracture path

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The research was sponsored by the National Science and Technology Major Project of China (No. 2017ZX04005001) and the Key Research and Development program of Shandong Province (2018GGX103053).