Improving the mechanical properties of Al-Ni-Fe alloys through friction stir processing

Friction stir processing as a relatively new and effective solid-state process is used for surface modification of metals and alloys in order to modify their microstructure and properties. In this study, the effect of friction stir processing on the microstructure and mechanical properties of an Al-0.9Ni-Fe alloy was investigated. The process was performed under the rotational speeds of 600-2000 rpm and the traverse speed of 25 mm/min. According to the results, the severe surface plastic deformation refined the intermetallic compounds present in the microstructure, improved their distribution within the matrix, and substantially reduced the amount of casting defects. As a result of these microstructural variations, the tensile strength and percent elongation of the base alloy are increased by almost 40 and 205%, respectively. The fracture toughness is also improved by 205%. It was also found that the hardness of processed alloy is about 24% higher as compared to the base alloy.