Fabrication of Mg/Al12Mg17 in-situ surface nanocomposite via friction stir processing

In this study, in-situ magnesium matrix surface nanocomposites were prepared by adding Al particles to an as-cast pure Mg ingot using friction stir processing (FSP). The effects of the number of FSP passes, tool design, rotational and travel speeds were investigated. Microstructural investigations showed a significant grain refinement owing to dynamic recrystallization. According to scanning electron microscopy examinations and X-ray diffraction results, Al12Mg17 intermetallics were formed during FSP due to chemical reaction at the Al-Mg interface. As a result of severe plastic deformation, the intermetallic particles formed at nanometre size. X-ray diffraction showed that the crystalline size of intermetallic particles reached ≤ 50 nm, due to high material flow during FSP. The intermetallic formation and grain refining led to an increase in the hardness values 1.5-3 times) that of the as-cast pure Mg ingot.