Research of the Secondary Phase Behavior of As-cast V-5Cr-5Ti Alloy

Abstract:

The as-cast state microstructure was analyzed by XRD、OM、SEM and TEM. The results show that V-5Cr-5Ti alloy was fabricated by vacuum electron-beam melting ,it has coarse grain, the grain has the characteristics of dendritic crystal made by lamellar secondary phase. The lattice parameters of metal vanadium and V-5Cr-5Ti alloy is 0.30316nm and 0.30375nm, the swelling of V cell volume is 0.58%. There are two kinds of the secondary phase in as-cast alloy:1) Short strip secondary phase, has FCC structure, the lattice parameter is 0.4182~0.4228nm; 2) Elliptical-shaped secondary phase, has FCC structure, the lattice parameter is 0.4186~0.4242nm; In the process of solidification, Ti and C formed metastable interstitial phase (Ti2C), which has FCC structure, or V and C formed metastable interstitial phase (V2C), which has HCP structure; Then, atoms substituted by each other. Finally, the secondary phases are vanadium and chromium-alloyed precipitations of titanium oxycarbonitride, which chemical formula can be expressed as (Ti2-CON).