Localized Microstructural Modification of Castings for High Performance and Repair

Friction stir processing (FSP) is being developed as a generic technique for microstructural modification. Being a solid-state process, it has the potential to improve mechanical properties significantly. The concept can be applied to convert cast microstructure to wrought microstructure. For cast components, this can lead to embedded regions of high mechanical properties. The effectiveness of FSP in enhancing mechanical properties of cast microstructure depends on the alloy chemistry and FSP thermal cycle. In this talk, a brief overview of results on aluminum and magnesium alloys will be presented. Examples include, 50% increase in static strength, 100% increase in fatigue strength and ductility improvement by many times. These examples lead to a microstructure-based design approaches for consideration of FSP. The key FSP parameters and physical metallurgy concepts governing the overall effectiveness will be highlighted. This basic approach can be extended to repair of castings.