Study on strengthening and toughening mechanism of Ti-Ni-Al ternary metallic-intermetallic laminated composites: Effect of interlaminar phase and Ti2Ni morphology

Further improving the strengthening and toughening properties of traditional binary metallic-intermetallic laminated (MIL) composites has become an urgent problem to be solved. In this work, a thin 0.02 mm Ni layer was added between the Ti and Al layers to prepare novel Ti-Ni-Al ternary MIL (TNA-TMIL) with multi-layer heterostructure (HS) characteristics, which significantly improved strength and toughness. TNA-TMIL composites include intermetallic layers (Ni-Al and Ni-Ti), unreacted metal layers (Ti-6Al-4V and Ni) and special morphology Ti2Ni in the Ti-6Al-4V layers. With the rise of hot-pressing temperature from 710 degrees C to 900 degrees C, the eutectoid reaction and the increase of Ni element in Ti-6Al-4V alloy caused the morphology of Ti2Ni in the Ti6Al-4V layer transition from island-like to network-like/needle-like to transition regions and finally formed needle-like Ti2Ni morphology. The electron backscatter diffraction (EBSD) analysis of the needle-like Ti2Ni shows that it has a weak cubic texture, and its fine grains are composed of dynamic recrystallization (DRX) and deformed grains. Nano-indentation and compression experiments indicated that the mechanical properties of TNA-TMIL composites are related to the different HS combinations and the morphology changes of Ti2Ni in the Ti-6Al-4V layer. This discovery may provide experience for designing and developing ternary MIL composites.