In recent years, the Me-Si-B (Me-metal) ternary systems have received considerable attention aiming at the development of high-temperature structural materials. Assuming that any real application of these materials will rely on multicomponent alloys, as is the case of Ni-base superalloys, phase equilibria data of these systems become very important. In this work, results are reported on phase equilibria in the V-Si-B system, and are summarized in the form of an isothermal section at 1600°C for the V-VSi 2 -VB region. Several alloys of different compositions were prepared via arc melting and then heat-treated at 1600°C under high vacuum. All the materials in both as-cast and heat-treated conditions were characterized through x-ray diffraction, scanning electron microscopy, and selected alloys via wavelength dispersive spectroscopy. A negligible solubility of B in the V 3 Si, V 5 Si 3 (T 1 ), and V 6 Si 5 phases as well as of Si in V 3 B 2 and VB phases was noted. Two ternary phases presenting the structures known as T 2 (Cr 5 B 3 -prototype) and D8 8 (Mn 5 Si 3 -prototype) were observed in both as-cast and heat-treated samples. It is proposed that at 1600°C the homogeneity range of T 2 extends approximately from 5 at.% to 12 at.% Si at constant vanadium content and the composition of D8 8 phase is close to V 59.5 Si 33 B 7.5 (at.%).

To determine the phase relations of various Me-Si-B (Me-metal) ternary systems we have been studying, it is necessary to experimentally re-evaluate the related Me-B binaries. The objective of this work is to report our data concerning the invariant reactions of the V-B system. The V-B alloys were prepared via arc melting and characterized through x-ray diffraction (XRD) and scanning electron microscopy (SEM). The liquid compositions proposed for the reactions L ↔ V ss + V 3 B 2 , L + VB ↔ V 3 B 2 , L ↔ VB 2 + B ss are, respectively: 12%, 19%, and 95% (at.% B).

No abstract

No abstract

No abstract