Through-Thickness Localized Strain Distribution and Microstructural Characterization of Functionally Graded Al/GNP Composite Fabricated by Friction Stir Processing

In the present study, the through-thickness functionally graded Al/GNP composite is fabricated by a novel single-step friction stir processing involving a step grooving approach. The digital image correlation technique reveals a variation in localized yield strength from 44 MPa at the surface to 49 MPa at the core giving a significant variation of 5 MPa within a short span of 2 mm (thickness) indicating the higher stiffness of the core region. The maximum strain value also ranges from 0.79 at the surface to 0.48 at the core of the composite signifying the strain accumulation near the FSP surface. The load transfer through the clean and semi-coherent interface between the GNP and Al matrix seems to have the dominant role in the localized strengthening of the core region. The property gradient indicates that the objective of fabricating the FGC is successfully realized by the proposed methodology.