Experimental Investigations on the Mechanical Properties and Microstructure of Al7075-TiN Nano-Composite Formed by Friction Stir Processing

Friction stir processing (FSP), originally based on friction stir welding, is believed to be a cost-effective solid state mechanical alloying technique very useful to produce composites. This makes use of a simple mechanical tool stirring and mixing material in localized region to cause dynamic recrystallization to produce new microstructures. In this study, FSP was applied to produce AL-TiNnano-composite with 7075-T6 aluminium as matrix phase. Three major parameters of the process, namely tool geometry, number of passes and tool rotation direction, were varied to realize the composite while the other parameters as penetration, tilt angle feed rate and rotational speed were kept fixed. In order to characterize the newly formed composite, various tests including optical microscope, SEM, EDS, XRD, micro-hardness, tension and wear tests (pin on disc) were performed in the FSP zone. The results showed that the FSP process produced TiN based composite of nano-size with various phases. The distribution of nano-particles was found to be dependent on the process parameters. The distribution of particles was tend to become uniform with increasing passes, alternative changing of tool rotation and threaded tapered tool. The grain size reduced significantly and followed the aforesaid trend in respect of effect of parameters. With particles distributed more evenly, the average hardness was found to be increasing. Further, the hardness was higher than the matrix material. However, ductility most probably due to presence of intermetallics in the composite reduced and the same was found to be true for tensile strength.The wear tests showed remarkable improvement in the wear performance of matrix material after processing with FSP (i.e., composite). The current study has shown that FSP can be employed as a useful tool to produce low-cost nano-composites with improved wear and mechanical properties satisfying the needs of modern engineering. Furthermore, this study will act as a guideline to the materials engineers to produce required materials with modifies properties. Keywords:Friction Stir Processing, Mechanical properties, Microstructure, Xrd, SEM, Hardness, Tensile, Wear, Nano-powder, composite, TiN, Al 7075