Specific Heat Capacity Measurements of Intermetallic Phases in the Ternary Al-Ti-Cr System

Abstract

Specific heat capacities of the γ-TiAl and τ phases in the Al-Ti-Cr system were determined in the temperature range between 298 and 773/873 K based on one binary (51.2Al-48.8Ti) and three ternary alloys (53Al-44Ti-3Cr, 64.6Al-30.2Ti-5.2Cr, 65.3Al-26.7Ti-8Cr). The specific heat capacity measurements in this system were performed for the first time. The measurements were carried out using heat-flux DSC devices employing the classical three step method. The measured heat capacities were lower than the approximation using the Neumann-Kopp rule. These differences in the heat capacity data arise probably due to the variation of the chemical bonding state between the intermetallic phases and the pure elements which are not taken into account by Neumann-Kopp’s rule. In order to check the reliability of the obtained results, the enthalpy increment was measured by using drop calorimetry. The heat increments determined using the drop calorimetry was in an excellent agreement with the enthalpy increments calculated using the analytic description of the heat capacities from DSC.