Additive friction stir deposition of al 7075 parts and the effect of heat treatment on microstructure, electroconductivity, and mechanical properties

Additive friction stir deposition (AFSD) is a relatively new metal additive manufacturing technique with many advantages compared to fusion-based methods. Despite the recent developments, the research about AFSD is in the initial stages, and processing hard and strong materials such as Aluminum 7075 is still challenging. In this study, a set of processing parameters is introduced and optimized for the AFSD of defect-free Al 7075 parts. Microstructure, electroconductivity, and mechanical properties of the as-deposited parts are studied. Compared with feedstock, the results indicated that the conductivity of the printed specimens increased by 19.5%, and the strength and hardness experienced a significant decrease by 54.4% and 43.5%, respectively. The change in the properties was associated with the precipitation enlargement and aggregation during the AFSD process. Subsequently, heat treatment was conducted to recover the mechanical properties, and noteworthy enhancements, a 101.2% increase in hardness and a 49.1% increase in strength, were recorded compared to the as-deposited condition due to the smaller and more uniformly distributed secondary phases in the matrix.