Thermal evidence for the structural instability in Ni3Al alloys

The thermal expansion of Ni3Al intermetallic compound is determined by a thermal dilatometer and simulated by the molecular dynamics method. The results of the linear thermal expansion coefficients are presented from 200 K up to the maximum temperature of 1600 K. The single phase of Ni3Al intermetallic compound is confirmed by x-ray diffraction together with DSC melting and solidification peaks, from which the solidus and the liquidus temperatures are obtained to be 1660 and 1695 K, respectively. The measured linear thermal expansion coefficient increases from 1.5 × 10 −5 to 2.7 × 10 −5 K −1 in the experimental temperature range, in good agreement with the data obtained by the molecular dynamics simulation, just a slight difference from the temperature dependence coefficient. Furthermore, the atomic structure and position are presented to reveal the atom distribution change during thermal expansion of Ni3Al compound.

show abstract

“…Ref. [25] Ref. [26] As a macroscopic characterization, thermal expansion is essentially caused by the atomic vibration in the lattice.…”

mentioning

confidence: 99%

Thermal Expansion of Ni ₃ Al Intermetallic Compound: Experiment and Simulation

Wang

Lü

Zhou

et al. 2016

Chinese Phys. Lett.

View full text Add to dashboard Cite

show abstract

“…Williams et al [19] have found no significant variation in well-annealed Ni 3 Al containing either 24 or 25 at.% Al. However, the measurements by Ramesh et al [20], up to 1000 C, have shown the CTE of Ni-24 at.% Al to be slightly lower than that of stoichiometric Ni-25 at.% Al. However, Rao et al [21] report that the CTE shows an increase with lower Al concentrations up to 1000 C, and attributes the increase to a larger number of vacancies at off-stoichiometric compositions.…”

Section: Cte Of Ni 3 Almentioning

confidence: 85%

Modelling the coefficient of thermal expansion in Ni-based superalloys and bond coatings

et al. 2016

View full text Add to dashboard Cite

The coefficient of thermal expansion (CTE) of nickel-based superalloys and bond coat layers was modelled by considering contributions from their constituent phases. The equilibrium phase composition of the examined materials was determined using thermodynamic equilibrium software with an appropriate database for Nibased alloys, whereas the CTE and elastic properties of the principal phases were modelled using published data. The CTEs of individual phases were combined using a number of approaches to determine the CTE of the phase aggregate. As part of this work, the expansion coefficients of the superalloy IN-738LC and bond coat Amdry-995 were measured as a function of temperature and compared with the model predictions. The predicted values were also validated with the published data for the single-crystal superalloy CMSX-4 and a number of other Ni-based alloy compositions at 1000 K. A very good agreement between experiment and model output was found, especially up to 800 C. The modelling approaches discussed in this paper have the potential to be an extremely useful tool for the industry and for the designers of new coating systems.

show abstract