Production of Al-Ti Composite by a Combination of Accumulative Roll Bonding and Friction Stir Processing

In this research, an in situ Al-Ti composite was fabricated by a combination of accumulative roll bonding (ARB) and friction stir processing (FSP). Following 3 cycles of ARB, FSP was performed for 5 passes with 16 mm min−1-line speed and 1600 rpm rotary speed. The structure and properties of the composite were investigated using an optical microscope (OM), scanning electron microscope (SEM), x-ray diffraction (XRD), hardness test, tensile strength, and abrasion test. It was found that with an increase in the number of ARB cycles, Ti layers were broken into smaller particles. Annealing after ARB caused the formation of initial Ti-Al intermetallic particles. Moreover, performing FSP on these samples led to the formation of a nanostructure containing Ti and Ti-Al intermetallic compounds in the Al matrix. XRD results showed that the titanium aluminides produced during FSP were TiAl3. XRD patterns also showed some unreacted primary Ti particles in the composites. The hardness of the ARB sample reduced remarkably after annealing at 600 °C for 180 min. The structure of the composite was refined, and its hardness increased after the FSP process. The maximum hardness was 81.4 BHN which was obtained after 3 passes of FSP. The tensile and yield strength of Al-Ti-AlTi3 composites increased from 89 to 140 MPa compared to annealed Al. Abrasion tests showed that the wear mechanism of ARB and FSP samples was a combination of adhesive and abrasive mechanisms.