Defect Elimination in Cast Al Components via Friction Stir Processing

Friction stir processing (FSP) is a novel process developed based on the principle of friction stir welding (FSW) that locally manipulates Hie microstructure by imparting a high level of energy in the solid state resulting in improved mechanical properties. Our work to date has shown that FSP can be implemented as a post-casting method to locally eliminate casting defects, such as porosity due to gas evolution during casting. Coarse second phase are broken into fine nearly equiaxed particles and distributed uniformly in the matrix; grain refinement is also attained by dynamic recrystallization during FSP. This results in improved tensile properties of the cast Al A206 alloy. Such improvements have important implications for manufactured components for diesel engines and for critical and high integrity components. The convenience of FSP as a post-processing step that can easily be carried out during machining operation makes it quite attractive for adoption.