The Effect of Aluminium Content on Thermophysical Properties of Ni-based Superalloys

抄録

Ni₃Al is the principal component in the γ′ phase formed in Ni-based superalloys but Ni₃Cr and Ni₃Fe can also contribute to the γ′ phase at temperatures below 820 K. Approximate values for the γ′ phase content can be derived from a relationship based on (mass% Al). In a previous publication it was shown that the density in both the solid and liquid alloys was dependent upon the γ′ phase (or Al) contents in the alloy. Consequently, the effect of the γ′ phase on other thermophysical properties (C_p, enthalpy, electrical resistivity, thermal conductivity and diffusivity) have been investigated. Linear relations were found between the property values around 300 K and the mass% Al. It was also found that property–temperature relationships were also affected by the γ′ phase (or Al) contents. Although it is known that the strong bonding between Ni and Al atoms affects the density of liquid alloys, we were unable to establish any such relationship for the other properties for liquid alloys because of the large experimental uncertainties in the measurements of these properties. This study has revealed that there is an urgent need for accurate values for C_p, electrical resistivity, thermal diffusivity and conductivity for liquid, Ni-based superalloys.