Effects of Multipass Additive Friction Stir Processing on Microstructure and Mechanical Properties of Al-Zn-Cup/Al-Zn Laminated Composites

A laminated composite of Al-Zn alloy reinforced with copper powder has been fabricated using friction stir additive manufacturing (FSAM). For this purpose, friction stir processing (FSP) was performed in one to four passes on Alclad Al-Zn aluminum alloy sheet. The results showed that, depending on the rotational and traverse speeds, a protective high-purity aluminum layer on the surface of Alclad Al-Zn emerged from the interface and formed an integrated protective layer in the areas around and away from the stir zone. An Al-Cu intermetallic (Al2Cu) layer formed at the interface of the large reinforcement particles. However, in smaller particles, the copper particle reacted completely with Al. Composite fabrication using a rotational speed of 800 rpm, traverse speed of 40 mm/min, and two passes resulted in a 26.3% increase in the maximum ultimate tensile strength (UTS) to 422.69 +/- 4.31 MPa and a 2.6% increase in elongation in 25.31 +/- 2.11% compared with a powderless double-layer sample.