Microstructure evolution and mechanical properties of Ti-Ni-Al ternary Metallic-Intermetallic Laminate (MIL) composites

Abstract

Metallic-Intermetallic Laminate (MIL) composites of Titanium-nickel-aluminum ternary system were fabricated and investigated for the microstructure evolution, reaction process, and mechanical property. The results show that Ni-Ti produces three intermetallics: Ni3Ti, NiTi, and Ti2Ni. Ni-Al produces four kinds of intermetallics in turn with the reaction: NiAl3, Ni2Al3, NiAl, and Ni3Al. The Ni-Al diffusion reaction rate is faster than that of Ni-Ti. The extent of the Ni-Al reaction is more affected by the reaction time, but the Ni-Ti reaction is more sensitive to temperature increase, which results from the α phase of titanium changing to the β phase when the temperature is higher than transition point, and Ni diffuses faster in β-Ti. Some special network-like, island-like structure and needle-like Ti2Ni organizations were found in the Ti6Al4V layer due to the different diffusion rates of Ni in the α and β phases of Ti6Al4V. Compression tests show that the mechanical properties of MIL are strongly correlated with the type and number of layers of Ni-Al intermetallic. The strength and toughness of the specimen reacted at 710 °C for 5 h are improved compared to the other specimens, the compressive strength and failure strain reached 1900 MPa and 0.35, respectively.