Investigation of hybrid friction stir processing for the simultaneous production of Al/Cu+TiO2 surface composite and surface alloy

The study investigates the fabrication of a hybrid aluminum-based surface composite and alloy using Al1050 as the base material, by dispersing copper and titanium oxide particles on its surface using the friction stir processing method. This novel approach to enhancing material properties combines surface alloying with composite fabrication. Optical microscopy of the samples reveals fine grain refinement, uniform particle dispersion within the matrix, and effective particle bonding. Microhardness analysis results indicate an increase in hardness in samples produced by both surface alloying and surface composite methods. An increased number of passes considerably enhances the hardness of the composite layer due to the pinning effect and the presence of hard TiO2 particles. The peak hardness (58.32 HV) and highest tensile strength (173.34 MPa) were achieved for the S33 sample (50% Cu, 50% TiO₂, processed with three passes). The strength of the samples shows a positive trend with the addition of reinforcing particles. The results demonstrate that by selecting an appropriate number of passes, both strength and ductility can be simultaneously improved. The highest strength and tensile extension achieved were 173.34 MPa and 19.45%, respectively. Wear resistance data also indicate that the addition of reinforcing particles and alloying powder enhances the samples wear resistance. With an increase in the number of passes from one to three, no structural defects were observed due to adequate heat generation and the stirring effect. Furthermore, the adequate interaction between the plastically deformed Al1050 matrix and the copper and TiO2 particles prevented defect formation. Microstructural images confirmed that TiO2 particles were uniformly dispersed within the Al1050 matrix and that the copper were well-dissolved in the aluminum matrix.