Abstract: The superplastic forming/diffusion bonding(SPF/DB) processes of multi-sheet structure of Ti2AlNb alloy are studied. The uniaxial tensile tests of Ti2AlNb rolled sheets are carried out by using constant strain rate method and the optimal superplastic forming condition is obtained which the temperature is 940 ℃ and the strain rate is 0.000 5 s1. The SPF of multi-sheet structures of Ti2AlNb alloy is simulated by using the software MARC. The thickness distribution and the possible defects of structures are predicted. The SPF/DB experiments of three-sheet structure and four-sheet structure are done which the loading pressure of SPF processes are the optimized p-t curves and the parameters of diffusion bonding are as follow：=940 ℃, p=10 MPa, t=180 min. The results show that the panel of three-sheet structure appears grooves whose depth and width are 4.49 mm and 8.85 mm respectively. The forming quality of four-sheet structure is better and the surface is smooth without wrinkles, grooves and other defects. The microstructure of the joint interfaces is observed which shows an excellent bonding at the interfaces. The study provides a reference basis for the manufacture of complex thin-walled sandwich structures in aerospace of Ti2AlNb alloy.

Key words: multi-sheet structure, numerical simulation, p-t curve, superplastic forming/diffusion bonding(SPF/DB), thickness distribution