Evaluation of TiAl3 Intermetallic Formation Mechanism and Revolution of Annealing Texture in Al/Ti Powder/Al Laminate Composite Fabricated by Cold Roll Bonding and Post-Annealing Treatment

In this paper, bulk sheets of multilayer Al-Ti composites were fabricated by cold roll bonding (CRB) at 50% thickness reduction and annealing in different conditions. The effects of annealing temperature and time on the bonding features of Ti-Al have been evaluated. The microstructural changes were studied by scanning electron microscopy (SEM) and focus ion beam microscope (FIB). A field emission electron microscopy (FEG-SEM) equipped with an electron backscatter diffraction (EBSD) tool was utilized to evaluate microstructural and textural changes. This study revealed that CRB composites of Ti-Al can produce the TiAl3 in relatively short times at annealing temperatures under the Al melting point. The results showed that just the TiAl3 intermetallic layer formed in the Ti/Al interface by 2 h annealing at 590°C. TiAl3 formation mechanism can be stated as following stages, Al phase elimination, Kirkendall voids formation, Ti and TiAl3 phase's volume increasing, micro-crack creation, and finally, easier formation of TiAl3. Mechanical evaluation of Al/TiAl3/Al layered composite showed that low ductility is related to growth and joining of Kirkendall voids around Al/TiAl3 interface that formed after a 2 h annealing at 590°C. Microstructural characterization by EBSD revealed annealing at this condition led to the creation of Al matrix with large grains (about 60 μm) and polycrystalline TiAl3 intermetallic containing small grains (average 5 μm). One of the main outputs from texture analysis is the recrystallization texture components changing after the formation of the TiAl3 intermetallic compound. The presence of large Ti aluminide particles resulted into the creation of a new strong P recrystallization texture component besides R5 and Q.