Metallurgy Commons^™

Characterization Of Residual Stress And Precipitate Evolution In Aluminum 2xxx Self-Reacting Friction Stir Welds, Benjamin Joe Wing

Doctoral Dissertations

2xxx series aluminum alloys possess attractive properties for structural aerospace applications including high strength to weight ratio, corrosion resistance, and stable cryogenic performance. Solid state joining processes are often employed to reduce weld defects and improve weld performance/consistency as many alloys of this range have poor weldability for traditional fusion based joining techniques. One such process, self-reacting friction stir welding (SRFSW) allows for consistent high-quality, welding of large and curved articles is often used in the construction of large structures such as launch vehicle liquid propellant tanks.

Despite the merits of this process, joint softening (a decrease in mechanical properties …

Effect Of Sc On Recrystallization Resistance Of Aa7050, Keaton Schmidt

Dissertations, Master's Theses and Master's Reports

The extrusion process involves high temperatures and strains that can result in undesirable microstructures, especially along the surface. Extruded alloys tend to exhibit surface recrystallization during heat treating at regions of higher strains, which can lead to reduced fatigue strength and corrosion resistance. By adding Sc to AA7050, nano-sized dispersoids are formed with Sc cores and Zr shells that restrict recrystallization more than the base alloy that only utilizes Zr. Billets with varying Sc content and a control with only Zr were cast, and extrusions were made in order to compare surface microstructures at varying strains in the as-extruded and …