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

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 TiO2. 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.