Abstract
The microstructure and mechanical properties of friction stir welded 7055 aluminium alloy under air cooling and water cooling are investigated by means of hardness and tensile testing, optical microscopy and transmission electron microscopy. Water cooling results in reduced softening in the weld zone and therefore higher tensile strength compared to air cooling. Fracture generally occurs within the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ) on the retreating side in joints welded under air cooling but shifts towards the TMAZ and nugget zone (NZ) in the joints welded under water cooling. The fracture surfaces are generally flat for the air-cooled joint, but exhibits a zig-zag feature for the water-cooled joint. The mechanical behaviour of the weld has been discussed in light of the change in grain structure and precipitation in the NZ, TMAZ and HAZ caused by cooling conditions.
| Original language | English |
|---|---|
| Pages (from-to) | 74-85 |
| Number of pages | 11 |
| Journal | Materials Characterization |
| Volume | 141 |
| Early online date | 22 Apr 2018 |
| DOIs | |
| Publication status | Published - Jul 2018 |
Keywords
- friction stir welding
- 7055 aluminium alloy
- cooling conditions;
- microstructure
- mechanical properties