Nb-Al Binary System: Reevaluation of the Solubility Limits of the (Nb), Nb3Al, Nb2Al and NbAl3 Phases at High Temperatures

Abstract

In this work a re-investigation of the solubility limits of the (Nb), Nb 3 Al, Nb 2 Al and the Nb-rich side of the NbAl 3 phases on the Nb-Al system is presented. Alloys in the binary fields ((Nb)+Nb 3 Al, Nb 3 Al+Nb 2 Al and Nb 2 Al+NbAl 3 ) were arc-melted, and then equilibrated at 1000, 1200 and 1400 °C. The phases were confirmed via X-ray powder diffractometry, and their compositions were determined via EPMA measurements. The results showed agreement with the literature concerning the solubility limits of (Nb), Nb 3 Al and NbAl 3 phases, while important differences in the values were found for the Nb 2 Al phase. In addition, the lattice parameters of the Nb 2 Al phase were determined via Rietveld refinement. This new set of more accurate experimental information indicates that a thermodynamic reassessment is necessary to precisely describe this system.

New Approach to the Compound Energy Formalism (Nacef)Part Ii. Thermodynamic Modelling of the Al–Nb System Supported by First-Principles Calculations

“…Reference Technique Index Temperature (Solidus/liquidus) Jorda et al [15] DTA/LTA A Stein et al [20] DTA A Wicker et al [14] DTA A Witusiewicz et al [1] DTA/PA A Zhu et al [19] DSC A Lundin and Yamamoto [12] DTA B Baron and Savitskii [10] TA B Svechnikov et al [13] TA B Phase solubility range Silva et al [6] EPMA A Menon et al [17] EPMA A Kokot et al [16] XRD A Shilo et al [18] KE A First-principle enthalpies (J/mol) of σ phase at 0 K. ΔH , resp. σ ΔH , correspond to results referred to fcc Al and bcc Nb, resp.…”

“…The Al-Nb system is an important binary system for the development of many structural materials or as coatings for high temperature applications. Based on inconsistencies between the most recent assessments [1,2] as well as data from heat-treated ternary alloys [2][3][4][5] containing Nb and Al, new investigations on the solubility limits of the intermetallic phases of the Al-Nb system were recently reevaluated by [6] via Electron Probe MicroAnalysis -Wavelength Dispersive Spectrometry (EPMA -WDS) from equilibrated alloys.…”

“…The electronic structure and total energy calculations were based on Density Functional Theory (DFT). The purpose of the present work is to provide an accurate thermodynamic description for the Al-Nb system taking into account the new experimental data given by [6] and using results from DFT calculations for compounds within the CALPHAD framework.…”

Sıcak Presleme Yöntemiyle Üretilen Nb Takviyeli Mg Matrisli Kompozitlerin Mikroyapı ve Mekanik Özellikleri

“…Matris alaşımı için karışımlarda ağırlıkça %5 Sn ve %4 Zn kullanılmıştır. Nb içerisinde ağırlıkça %7,4 oranına kadar Al alaşım elementi çözünebilmektedir [35]. Bu nedenle, içeriğinde Al içermeyen Mg-Sn-Zn alaşımı matris olarak seçilmiştir.…”

Phase Transitions in the Co–Al–Nb–Mo System

“…To determine the phase equilibria in the Co-Al-Nb-Mo system, data on the following three ternary systems: Co-Al-Mo, Co-Nb-Mo, and Co-Al-Nb may be used [1,[4][5][6][7]. The phase analysis in binary phase diagrams Al-Mo [8], Co-Mo [9], Co-Nb [7,9,10], Co-Al [11], Nb-Mo [12], and Nb-Al [7,13] may also be used.…”