The solid state diffusion bonding of the Ti-6Al-4V alloy was carried out in inert gas environment and the oxidation behavior at high temperatures was investigated. Bonding was conducted in a furnace using selected combinations of temperature ranging from 850 to 950 degrees C, pressure of 3 MPa for 1-3 h in argon gas environment. Good diffusion bonding interface have been observed at relatively low temperature and pressure. The microstructure bonded at 900 degrees C exhibits oxygen-enriched alpha phase at bonded interface. It is shown that at the optimum condition for diffusion bonding with parent metal. the oxide film becomes unstable and the oxygen is diffused into the bulk. The evidence of nucleation of new grains and microhardness properties at the interface proves the diffusion bonding process is successful. (C) 2006 Elsevier B.V. All rights reserved.