Ti-5Al-2.5Mo-1.4V rolled plates were subjected to solid-solution heat treatment at 870 or 930 degrees C for 1 h and aged for 1-8 h at 460 degrees C to investigate the relationship between the microstructure and the vibration characteristics of the alloy. According to the experimental results, the S870 solid solution matrix contains alpha + alpha' + beta structures and the S930 solid solution specimen possesses alpha + alpha' structures (beta transus is similar to 900 degrees C). Increasing the alpha' phase content improves strength and hardness but reduces ductility. It also promotes internal friction and thus increases damping. During the 460 degrees C aging process, the alpha' phase in the region of S870/Ah grows and transforms into a finer needle structure and the primary alpha phase (bounded by prior beta grain boundary) of S930/Ah grows within the alpha' matrix. Both S830/Ah and S930/Ah reveal similar tendencies in mechanical properties with increased aging time. When the aging time exceeds 1 h, S870/Ah, having a large quantity of beta phase, has a better vibration damping ratio than S930/Ah (containing a great quantity of primary a phase). (c) 2005 Springer Science + Business Media, Inc.