Thermodynamic properties and diffusion thermodynamic factors in B2-NiAl

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Vol. 35; no. 5; pp. 867 - 876
• Main Authors: BENCZE, L, RAJ, D. D, KATH, D, OATES, W. A, SINGHEISER, L, HILPERT, K
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01.10.2004; Springer Nature B.V
• Subjects: Aluminum alloys; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diffusion; Entropy and other thermodynamical quantities; Exact sciences and technology; Mass spectrometry; Materials science; Metallurgy; Nickel alloys; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of metals and alloys; Physics; Temperature; Thermal properties of condensed matter; Thermal properties of crystalline solids; Thermodynamic properties; Thermodynamics; Nickel base alloys; Knudsen effusion; Phase diagrams; Intermetallic compounds; Thermodynamic activity; Mass spectroscopy; Binary systems; Experimental study; Vaporization; Partial pressure; Aluminium alloys; Temperature effects; Diffusion process; Thermodynamic analysis; Diffusion; Thermodynamic properties; Partial molar quantity
• ISSN: 1073-5615; 1543-1916
• DOI: 10.1007/s11663-004-0081-x

The vaporization of Ni-Al alloys has been investigated in the temperature range 1178 to 1574 K by Knudsen effusion mass spectrometry (KEMS). Thirteen different compositions have been examined in the composition range 38 to 57 at. pct Al. The partial pressures and thermodynamic activities of both Ni and Al have been evaluated both directly from the measured ion intensities for a component in both the alloy and the pure element, I+M/I+oM, and also from the ion intensity ratios of the alloy components, I+Al/I+Ni, by means of a Gibbs-Dubem integration. Reliable partial molar enthalpies and entropies for both components have been obtained by mass spectrometry for this system for the first time. Both properties are found to be nearly temperature independent over the wide temperature range investigated. Two separate component diffusion thermodynamic factors have also been evaluated for the first time by taking into account the large vacancy concentrations in these alloys. The enthalpy and Gibbs energy of mixing of stoichiometric Ni0.5Al0.5 at 1400 K, evaluated using the Gibbs-Duhem ion intensity ratio (GD-IIR) method, are -78.4 plus/minus 1.2 and -49.0 kJ/mol, respectively, with Al(liquid) and completely paramagnetic Ni(fcc, cpm) as reference states.