Growth characterisation of TiAl3 during initial period of hot dip aluminising on Ti6Al4V

Abstract

ABSTRACT The interface reaction between solid titanium alloy and liquid aluminium is critical to understanding the evolution of the intermetallic compound (IMC) in brazing and weld brazing processes of titanium to aluminium dissimilar alloys. In this study, hot dip aluminising of solid Ti6Al4V under different temperatures was conducted to reveal the influence of reaction temperature and time on interfacial IMCs. Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA) and X-Ray Diffraction (XRD) were employed to investigate the interfacial microstructures and phases. The dominant IMC at the interface was identified to be TiAl3. With increasing dipping temperature and time, the thickness of TiAl3 increased. The TiAl3 layer grew parabolically and its growth was governed by a diffusion mechanism. A deviation from the normal parabolic to a smaller n value (n = 0.2) was observed and an activation energy of 71.6 kJ mol−1 was obtained. Both aluminium and titanium atoms were diffusing species through the TiAl3 layer. Grain coarsening of the TiAl3 and the existence of vanadium in the IMC possibly led to the deviation in the present study from the normal parabolic laws.