Effects of Short-Time Heat Treatment on Microstructure and Mechanical Properties of 7075 Friction Stir Welded Joint

The effect of short-time heat treatment on the microstructure and mechanical properties of a joint welded by friction stir welding (FSW) was investigated in a 7075 Al alloy. Short-time post-solution and aging treatment promoted recrystallization in the thermal–mechanical affect zone and did not lead to severe grain coarsening in the nugget zone (NZ) of the FSW joint. Solution treatment for 10 min and subsequent aging treatment for 3 h led to the precipitation of high-density η′ phases in the FSW joint. Short-time post-solution and aging treatment enhanced the hardness of HAZ and NZ of the FSW joint and improved the strength of this joint. The yield strength of the FSW joint after solution and aging treatments reached 465 MPa, and its welding efficiency was 89.2%.