New strategy for enhancing the strength and toughness of Ti-Al metallic-intermetallic laminated composites: Constructing multiple heterostructures using Ni foil

Abstract

In order to simultaneously improve the strength and ductility of Ti-Al metallic-intermetallic laminated (TA-MIL) composites, novel Ti-Al-Ni ternary MIL (TAN-TMIL) composites with multiple heterostructures (HS) were fabricated by adding a 0.02 ​mm Ni foil behind the Ti and Al foils. The results showed that TAN-600 consisted of the same phases (Ti, Al₃Ti, and Al) as TA-600 and additionally produced new NiAl₃ and Ni₂Al₃ phases due to the Ni-Al reactions. Furthermore, when the hot-pressing temperature was increased to 650 ​°C, Kirkendall voids appeared in the Al₃Ti layer (TA-650) and at the Al₃Ti/NiAl₃ interface (TAN-650). Compared to TA-MIL composites, the thickness of the Al₃Ti layer in the TAN-TMIL composites increased by four times when prepared at 600 ​°C, but decreased by four times when prepared at 650 ​°C. Electron backscatter diffraction (EBSD) and nano-indentation tests revealed that TAN-600 had multiple HS and more high-angle grain boundaries (HAGB), optimizing the structure of TA-600. Importantly, this structural arrangement enhanced the interface effects and compressive properties of TAN-600. Tensile testing indicated that the crack-free NiAl₃/Ni₂Al₃ layer contributed to the strength of TAN-600, ensuring multi-directional fracture in the Al₃Ti layer. This research provides insights for improving the strength and toughness of TA-MIL composites.