[en] Joining of TiAl to Ti alloy is a potential requirement for manufacturing the components with dual properties. In this paper, the hot-press bonding of Ti-33Al-3V to TC17 was implemented at different pressures and the temperature of 850 °C for 10 min with post bond heat treatment. The influence of pressure on interfacial microstructure evolution and atomic diffusion was analyzed in detail. The microstructure observation and phase composition analysis on the bond indicate that the metallurgical bonding of Ti-33Al-3V/TC17 is produced at pressures of 23–50 MPa, and an interfacial zone with a certain width forms between base alloys. A new α₂ (Ti₃Al) phase is generated in the interfacial zone. The influence of pressure on the metallurgical bonding of Ti-33Al-3V/TC17 includes two aspects. One is to promote the void shrinkage in the interfacial zone. The quantitative analysis of voids shows an increase in pressure induces a decrease in amount and size of voids. The highest bonding ratio of 96.3% can be obtained at the pressure of 50 MPa with post bond heat treatment. The second is to promote the atomic diffusion across bond line. The diffusion distances of Ti and Al atoms increase with an increase in pressure and the width of the interfacial zone shows a linear increasing law with the pressure. Moreover, a higher pressure induces a higher increment in atomic diffusion distance and width of the interfacial zone in the post bond heat treatment. - Highlights: • The new α₂ (Ti₃Al) phase is generated in the interfacial zone. • The width of the interfacial zone shows a linear increasing law with pressure. • An increase in pressure promotes void shrinkage to increase the bonding ratio. • The diffusion distances of Ti and Al increase with the increase in pressure. • Higher pressure causes a higher increment of atom diffusion distance after heating.