Hardening of the 1565ch Aluminum Alloy Surface by Friction Stir Treatment

Friction stir treatment of aluminum alloys performed without introducing high-strength particles is investigated. Rational friction stir parameters, including a tool rotation speed of 850 rpm and a linear speed of 25–40 mm/min, are determined experimentally. The influence of the tool pin length on the required sizes of the heat-affected and deformation zones is studied. A tool pin length of 1.5–2.0 mm is identified as the most effective. During friction stir treatment, a bowl-shaped treatment zone with uniformly expanding boundaries toward the workpiece surface forms. This treatment results in the fragmentation and uniform distribution of primary intermetallic phase particles. An ultrafine-grained structure with an average grain size of (2.30 ± 0.05) μm is observed in the stir zone. For flat specimens, an overlap of 0.25–0.33 for adjacent passes is recommended.