A New Approach to Direct Friction Stir Processing for Fabricating Surface Composites

Abstract

Friction stir processing (FSP) is a green fabrication technique that has been effectively adopted in various engineering applications. One of the promising advantages of FSP is its applicability in the development of surface composites. In the current work, a new approach for direct friction stir processing is considered for the surface fabrication of aluminum-based composites reinforced with micro-sized silicon carbide particles (SiC), eliminating the prolonged preprocessing stages of preparing the sample and filling the holes of grooves. The proposed design of the FSP tool consists of two parts: an inner-threaded hollow cylindrical body; and a pin-less hollow shoulder. The design is examined with respect to three important tool processing parameters: the tilt angle of the tool, the tool’s dispersing hole, and the tool’s plunge depth. The current study shows that the use of a dispersing hole with a diameter of 6 mm of and a plunge depth of 0.6 mm, in combination with a tilting angle of 7°, results in sufficient mixing of the enforcement particles in the aluminum matrix, while still maintaining uniformity in the thickness of the composite layer. Metallographic examination of the Al/SiC surface composite demonstrates a uniform distribution of the Si particles and excellent adherence to the aluminum substrate. Microhardness measurements also show a remarkable increase, from 38.5 Hv at the base metal to a maximum value of 78 Hv in the processed matrix in the surface composites layer. The effect of the processing parameters was also studied, and its consequences with respect to the surface composites are discussed.