The Polythermal Section of Ti-22Al-xNb (30-78at.%Ti) in Ti–Al–Nb System

Abstract

The polythermal section of Ti-22Al-xNb (30–78 at.% Ti) in the Ti-Al-Nb system was studied using X-ray diffraction analysis (XRD), differential thermal analysis (DSC), and electron probe micro-analysis (EPMA). No new ternary compounds were found in this work. The polythermal section has five three-phase regions, nine two-phase regions, and three single-phase regions. The O phase transition is confirmed to occur below 1000 °C. A four-phase invariant reaction β + σ → O + δ was found at 931 °C.

Phase Equilibria in the Ti-Rich Part of the Ti-Al-Nb System—Part I: Low-Temperature Phase Equilibria Between 700 and 900 °C

“…They derived local phase equilibria from extrapolations to phase interfaces obtained in a diffusion multiple consisting of Ti, Nb, Ti-73Al, Ti-40Nb, and Ti-60Nb annealed at 900 °C for 6000 h. No experimental sections for 700 and 800 °C were reported in the literature. Some information on equilibria at these temperatures is available from vertical sections reported in the literature, but almost all of them are limited to the range of the O phase along constant Al contents of 22 at.%, [19,[25][26][27] 25 at.%, [28][29][30] and 27.5 at.%. [31] Only exceptions are a vertical section along 50 at.% Ti from Bendersky et al [32] and a section along 8 at.% Nb presented by Xu et al [33] However, in case of the 50 at.% Ti section, this is only an estimated schematic based on two alloys.…”