Liquidus surface projection and isothermal section at 1500 °C of (Mo-5Nb)-Ti-C pseudo-ternary system

Abstract

The liquidus surface projection and isothermal section at 1500 °C of the (Mo-5Nb)-Ti-C pseudo-ternary system were experimentally determined. X-ray diffraction analysis and scanning electron microscopy in conjunction with electron-probe microanalysis were carried out to analyze the solidification behavior and phase constituents. The replacement of 5 at.% Mo with Nb was found to negligibly affect the solidification path or the formation of new phases. However, the quasi-peritectic point U2 shifted closer to the (Mo-5Nb)-C border in the liquidus surface projection than in the Mo-Ti-C system. The BCC single-phase region, BCC + TiC two-phase region, and BCC + Mo2C + TiC three-phase region were determined in the isothermal section at 1500 °C. The replacement of 5 at.% Mo with Nb was found to expand the BCC + TiC two-phase region and narrow the BCC + Mo2C + TiC three-phase region by stabilizing the TiC phase. Therefore, the addition of Nb to the Mo-Ti-C system expanded the compositional range of the BCC + TiC two-phase region, leading to variable properties of TiC-dispersed BCC-based alloys and BCC-TiC cermets.