The Keystone and MSU team propose to build on the successful feasibility demonstration conducted during Phase I to complete the development of solid-state joining of high strength and temperature alloys utilizing the Thermal Stir Welding process. The focus alloy for this project is Haynes 230; the alloy of choice typically utilized in rocket engine nozzel skirts. This class of alloy is difficult to fusion weld and with the successful Phase I demonstratipon has now been shown weldable using solid-state methods. Therefore, the Keystone team is proposing to utilize a Thermal Stir Welding process; a solid-state welding process that decouples the stirring and heating features of the process to enable optimization of each key process parameter. By independently controlling and optimizing these process parameters, the best metal working parameters can be established and utilized to plasticize and stir the Hanyes 230 alloy. Achievement of this objective will enable superior mechanical properties in the weld joint and thus maximize the capability of the weld for the intended application. During Phase II the Keystone team will complete process development and demonstrate TRL-4 readiness by producing a 24" diameter subscale nozzel skirt for testing and evaluation by NASA.