The effect of friction stir processing on the microstructure and mechanical properties of AF/C458 aluminum lithium alloy

• Main Author: Giles, Tanya L.
• Other Authors: McNelley, Terry
• Format: Others
• Published: Monterey California. Naval Postgraduate School 2012
• Subjects: Lithium alloys; Aluminum alloys; Mechanics; Metallurgy; Mechanical engineering
• Online Access: http://hdl.handle.net/10945/2041

Aluminum-lithium alloys have been under development for lightweight - high strength aerospace structures but implementation has been slowed significantly because of poor short transverse fracture toughness and brittle intergranular delamination cracking. The alloy AF/C458 (now designated AA 2099) has been designed to exhibit decreased mechanical anisotropy and improved fracture toughness while maintaining ductility and strength levels. This thesis examines the application of Friction Stir Processing (FSP) of AF/C458 as an approach to refine and homogenize the grain structure and enhance mechanical properties. FSP of peak-aged material results in refined, equiaxed grains but with reduced hardness due to the heat input of the process. The effect of post-FSP heat treatment has been established and the influence of FSP on tensile and fatigue properties has been determined.