Activity measurements on the Al-rich region of the Ni–Al system – A high temperature mass spectrometric study

• Published in: International journal of materials research Vol. 97; no. 4; pp. 461 - 470
• Main Authors: Narasimhan, Tiruppatur Subramaniam Lakshmi, Kath, Dieter, Markus, Torsten, Hilpert, Klaus
• Format: Journal Article
• Language: English
• Published: Munich De Gruyter 01.04.2006; Hanser
• Subjects: Activities; Applied sciences; Exact sciences and technology; Knudsen effusion mass spectrometry; Metals. Metallurgy; Nickel aluminides; Partial and integral molar properties; Activities; Nickel base alloys; Temperature; Intermetallic compound; Nickel Aluminides; Aluminium alloy; High temperature; Partial and integral molar properties; Mass spectrometry; Knudsen effusion mass spectrometry
• ISSN: 1862-5282; 2195-8556
• DOI: 10.3139/146.101239

Systematic vaporisation studies on the Ni–Al system with 0.32 x(Ni) 0.50 were carried out in the temperature range 1077–1592K by Knudsen effusion mass spectrometry. While Al(g) was the vapour species observed over all the samples, Ni(g) was also detected over samples with the compositions x(Ni)=0.50 and 0.49. From the p(Al)–T relations, activities of Al, and subsequently activities of Ni (by Gibbs–Duhem integration) were obtained. Moreover, partial and integral molar enthalpies and Gibbs energies of formation were evaluated. The variation of activities and other thermodynamic properties with composition are discussed. The enthalpy and Gibbs energy of formation of Ni Al (s) at 298.15K were obtained as = −62.1 4.2kJ mol and = −57.71.2kJ mol , respectively. This is the first time that a systematic mass spectrometric investigation has been carried out on the aluminium rich region of Ni–Al system where the vacancy concentration in the NiAl phase can be as high as 10%.