Journal of Materials Science, Vol.56, No.8, 5283-5295, 2021
Friction stir welding of novel T-phase strengthened Zn-modified Al-Mg alloy
Friction stir welding is extensively used in aluminum alloys for advanced engineering applications. A current challenge for 5 x x x series alloys is their poor welding strength due to the lack of hardening precipitates. Here we report Zn-modified novel Al-Mg alloys with Zn/Mg ratio below 1.0. Compared with 5 x x x series alloys, the strength of the welded alloy can be increased by 100 MPa owing to the distribution of T-Mg-32(AlZn)(49) hardening precipitates during friction stir welding and the subsequent heat treatment after welding. Fine spherical T '' precipitates and coarsening polygonal T ' precipitates are both observed at the thermo-mechanically affected zone. The bimodal distribution of the precipitates and the widest precipitate-free zone weakened the strength of this region, and thus the welded alloys are fractured at this area. The novel alloy with T precipitates is expected to further stimulate the researchers to improve the properties of traditional 5 x x x series alloy.