The high temperature bulk modulus of aluminium: an assessment using experimental enthalpy and thermal expansion data

There exists a certain ambiguity with regard to the actual high-temperature bulk modulus of aluminium. In particular, there is a considerable disparity between various single crystal elastic constant measurements. This point has not been addressed on the theoretical front as well. In view of this situation, we seek to assess the existing bulk modulus data for their internal thermodynamic consistency and also obtain a reliable estimate using experimental data on thermal expansion, enthalpy and specific heat. The procedure adopted for this purpose makes use of a thermodynamic framework that relates thermal and elastic properties through Gruneisenʹs hypothesis. The present analysis suggests that the oft-cited data of Gerlich and Fisher and the older one due to Sutton are not fully consistent with the existing thermal property data. The more recent data of Tallon and Wolfenden, although in better consonance with the requirements of thermodynamic consistency, are also found to be less reliable. A fresh calculation of the bulk modulus is made such that the estimated values exhibit a high degree of thermodynamic legitimacy with the selected thermal property data.