Thermal evidence for the structural instability in Ni3 Al alloys


Ramesh, R. and Pathiraj, B. and Kolster, B.H. and Maas, J.H. (1992) Thermal evidence for the structural instability in Ni3 Al alloys. Materials Science and Engineering A: Structural materials, 152 (1-2). pp. 60-66. ISSN 0025-5416

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Abstract:The thermal expansion coefficient (¿) and calorimetric data were obtained as a function of temperature in order to clarify some of the significant variations reported with regard to these values in the literature. Stoichiometric and off-stoichiometric compositions of Ni3Al alloys (with and without boron addition) were investigated. Dilatometric experiments were performed on all the alloys and the ¿ values were estimated over the temperature range from ambient to 1000°C. Two runs were made on each sample under different initial conditions and differences in ¿ values were noticed. The results were analysed based on our earlier X-ray diffraction results. Additional isothermal dilatometric tests were also carried out and a significant volume change was noticed (0.45% contraction) when the alloy quenched from 1000°C was heated to 600°C and held for a long duration. The calorimetric data were obtaindd over the same range of temperature and enthalpy changes, though less distinct, were noticed at around 360, 660 and 900°C. The variations seen further augment our earlier results on the instability of the L12 structure and the existence of a structural transformation
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Copyright:© 1992 Elsevier Science
Engineering Technology (CTW)
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