Fabrications of Surface Nanocomposite by Friction Stir Processing to Improve Mechanical and Microstructural Properties of Low Carbon Steel

Friction stir processing was used to fabricate metal matrix composites on the surface of low carbon steel. In this research for making 2 mm surface MMC, the groove method was applied to fabricate TiB₂ nanocomposite via cylindrical tool made of tungsten carbide. Microstructural properties of FSPed samples were studied by optical microscopy and scanning electron microscopy. To evaluate mechanical properties, the micro hardness and tensile properties of MMC were measured. The results indicated that the surface nanocomposite produced by this method had excellent properties. The microstructure of surface MMCs became fine (ferrite grain size became about 1–2 µm) with no defect and porosity. Moreover by adding TiB₂ nanoparticles to the low carbon steel matrix alloy, mechanical properties were improved. Micro hardness can become 200HV higher than that of the base metal. The surface nanocomposite also exhibited better tensile strength when sample yield stress increased to about 28 %.