Mechanical properties and microstructures of high-chromium V-Cr-Ti type alloys

Abstract

The mechanical properties of V-Cr-Ti type alloys depended on heat treatment conditions and Cr concentrations. In this paper the correlation between mechanical properties and heat treatment conditions as a function of Cr concentrations was explored using mini-size Charpy impact tests and microstructure observations. Vanadium alloys evaluated were V-xCr-4Ti (x=4, 7, 10, 12, 15, 20). Microstructure observations using transmission electron microscope (TEM) were performed to characterize the precipitates. The typical precipitates in the V-xCr-4Ti alloys were identified as Ti(C,O,N) and TiO 2. Ti(C,O,N) was observed in specimens annealed between 900 and 1000 °C and TiO2 was between 1100 and 1200 °C. The DBTT of V-(4,7)Cr-4Ti alloys was around -190 °C, while DBTT for the other alloys were above -30 °C. It is proposed that formation of precipitates larger than 400 nm in diameter found in the alloys containing more than 10% of Cr as well as solution hardening of Cr are affected to the increase of the DBTT of the alloys. © 2004 Elsevier B.V. All rights reserved.