Effects of Si addition on mechanical properties of Ti-5Al-5V-5Mo-3Cr alloy

In this paper, the ageing response and the mechanical properties of 11-5553 (Ti-5Al-5V-5Mo-3Cr) and Ti-5553s (Ti-5Al-5V-5Mo-3Cr-0.4Si) alloys are comparatively investigated. During ageing at 650 degrees C, the hardness of the alloys first increases in 30 min and remains constant from 1 h to 8 h, and then decreases with further increase the ageing time to 29 h. This variation is related to the chemical composition and the volume fraction of alpha phase. The mechanical properties of the 5 h aged Ti-5553 and Ti-5553s alloys are investigated, and the result shows that the ultimate tensile strength of the Ti-5553s alloy is higher than that of Ti-5553 alloy while the ductility of the Ti-5553s alloy slightly decreases. The tensile fracture of the Ti-5553s alloy shows a mixed model of intergranular fracture and cleavage fracture. (C) 2012 Elsevier B.V. All rights reserved.