Influence of microstructure on macroscopic elastic properties and thermal expansion of nickel‐base superalloys ERBO/1 and LEK94

In the present work the thermal expansion and the elastic properties of second generation nickel‐base superalloy single crystals ERBO/1 (CMSX‐4 variation) and LEK94 have been studied between about 100 K and 1273 K using dilatometry and resonant ultrasound spectroscopy, respectively. Inhomogeneity related to the large scale microstructure of the samples can act as a potential source of scatter for the propagation of ultrasonic waves. This can be overcome by choosing samples of sufficient size so that they appear as homogeneous media at the scale of the elastic wave length. Our final results are in good agreement with data reported in literature for similar alloy systems. In particular, the elastic material properties are only weekly affected by moderate variations in chemical composition and microstructure. Taking into account literature data for other superalloys like CMSX‐4, we derive general polynomial functions which describe the temperature dependence of the elastic moduli E_〈100〉, E_〈110〉 and E_〈111〉 in nickel‐base superalloys to within about ±3%. It was also observed that the alloys ERBO/1 and LEK94 show weak but significant anomalies in both thermal expansion and temperature coefficients of elastic constants above about 900 K. These anomalies are probably related to the gradual dissolution of the γ′‐precipitates at higher temperatures.