A clarification on local microstructural inhomogeneity in friction stir additively manufactured functionally graded composite materials

Abstract

A microstructure gradient functionally graded composite structure (MG-FGC) with Al2O3particle reinforcement within the additive layers of different grades (7475-T761, 5083-O, and 6061-T6) of aluminium alloys is successfully fabricated. It has been observed that the properties are spatially varied within the additive layers of the fabricated MG-FGC. The presence of the different sizes of the reinforcement Al2O3particles further causes the local deformation and microstructural inhomogeneity. The electron backscattered diffraction (EBSD) results show evidence of recrystallization followed by grain coarsening at the large-size particle/matrix interface, while smaller Al2O3particles are surrounded by the smaller equiaxed grain structure. This shows that the size and morphology of the Al2O3 particles affect the microstructural development. Therefore, understanding the physics related to the microstructural evolution affected by the size/morphology of Al2O3particles needs to be clarified.