Understanding Microstructure Evolution and Control During Hot Deformation: Application to Solid State Joining of High Strength Alloys

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The aim of the present project is to gain a better understanding of the governing mechanisms controlling microstructure evolution during solid state joining, specifically, linear friction welding. The latter is a promising manufacturing technology, which allows the production of near net shape components and joining of dissimilar materials. Both topics are of high importance to manufacturing industry as their widespread applications will result in lower scrapped material, shorter 'time-to-market' and lower life cycle cost of products. However, major questions regarding the relationships between process parameters (including the severe deformation phase during the process) and microstructure evolution and their combined influence on fatigue life of the joint, remain to be addressed. In parallel, successful transition from laboratory findings to industrial size components requires more realistic simulation tools, that can also take into account microstructure evolution as a function of process parameters. The project inscribes in this context and is aimed to develop a material model that will include microstructure evolution. An Ultra High Strength Steel, used for aircraft landing gear applications, and a new superalloy, developed for aircraft disk and blade applications will be used in the present investigation. The evolution of the microstructure will be studied using optical and scanning electron microscopies. Post weld heat treatments will be applied and their influences on mechanical properties of the joint, including its fatigue life, will be examined. The benefits of the work will extend beyond the aerospace industry to other Canadian industries, such as automotive, rail and oil and gas where these alloys are used and solid state joining is applied for many components. Moreover, two PhD and two Masters students will be trained during the course of the project.