An experimental study on multi-pass friction stir processing of Al/TiN composite: some microstructural, mechanical, and wear characteristics

TiN is an exceptionally hard and a wear-resistant ceramic. In the present work, the effect of mixing TiN particulates into the Al7075-T651 alloy was studied by employing a novel material fabrication technique called friction stir processing (FSP). The FSP was carried out using three different tool geometries (namely square, triangular, and threaded taper) with an objective to fabricate the Al/TiN composite with an appropriate set of mechanical and wear properties. A number of microstructural, mechanical, and wear tests were carried out in order to characterize the composite. In comparison to the parent metal, each of the composite specimens showed improved wear and friction performance. However, the improvement in the hardness was realized only with the threaded tool and that in the tensile strength was observed with the square tool, thus revealing a tool-property relationship in FSP. Contrarily, the ductility of all of the composite specimens was lower relative to that of the parent metal. A suitable trade-off among various characteristics was realized when FSP was performed using the square tool. The microscopic and energy dispersive spectroscopy (EDS) analyses showed that the dominant wear mechanism in the composite was adhesion. This study is the first report on the FSPed Al/TiN composite.