Effect of temperature on the interfacial evolution of Ti/Ni multi-layered composites fabricated by ARB

Abstract

The interface evolution of Ti/Ni multi-layered composites produced by accumulative roll bonding after heat treatment was investigated in this study. The influence of heat treatment temperature on the microstructure and chemical composition of the Ti/Ni interfaces were examined by scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy system (EDS) and transmission electron microscope (TEM). Phase composition and transition behavior of interfaces of the Ti/Ni multi-layered samples were studied by X-ray diffraction (XRD) and a differential scanning calorimeter (DSC). Only from the viewpoint of ΔG, ignoring the impact of other factors, the formation sequence of Ti–Ni IMCs is TiNi3→Ti2Ni→TiNi at the beginning of the diffusion reaction. With temperature increases, the microstructure of the composite is a mixture structure with alternating TiNi and Ti2Ni layers and the boundary morphology of each diffusion sub-layer transforming from an initial smooth and clear boundary, to the flocculent structure of the TiNi and Ti2Ni transition layer. The DSC results revealed a good martensitic and reverse transformation behavior from B2 to B19’ of Ms at around 64 °C. With temperature increases, the austenite transformation temperature (TA) slowly shifts to high temperature and the change of martensite transformation temperature (TM) is not obvious. The phase transition hysteresis (Ap-Mp) from 5.9 °C of the 550 °C × 10 h heat treatment sample increases to 33 °C of the 770 °C × 10 h sample.