Mechanical and Damping Behavior of Age-Hardened and Non-age-hardened Al Alloys After Friction Stir Processing

This study investigated the microstructure, mechanical, and damping properties of a non-age-hardened Al alloy (5086) and an age-hardened Al alloy (7075) after friction stir processing (FSP). Microstructural analyses indicate that FSP led the grain refinement of samples, and the grains size decreased with the decrease in the tool rotation rate. Furthermore, FSP with low rotation rate promotes the eta phase precipitation in the 7075 alloy, causing the micron-sized particles in the 5086 alloy to break up. After being subjected to FSP with low rotation rate, the 5086 and 7075 alloys exhibited excellent mechanical and damping properties. Such improved properties were ascribed to their equilibrium grain boundaries, fine grain, low density of dislocations, high fraction of high misorientation angle, and uniform particle distribution.