Temperatures- and Pressure-Dependent Thermostructural Properties of Ti2AlC MAX-Phase Using Quasi-Harmonic Debye Approximation

Abstract

A first principle study was performed to investigate the electronic and thermostructural properties of the Ti₂AlC MAX-phase using quasi-harmonic Debye approximation. The thermodynamical properties of Ti₂AlC MAX-phase at various temperatures and pressure were calculated via the quasi-harmonic Debye approximation and explored the role of temperature and pressure on heat capacity, bulk modulus, thermal expansion coefficient, Debye temperature, enthalpy, entropy, and Gibbs free energy. Surprisingly, both the bulk modulus and Debye temperature was observed to drop with increase in temperature. However, a rise in both occurred as the pressure gradually builds up. This suggests that the heat capacity is influenced by pressure and temperature in opposing ways. The observation of increase in both heat capacities (C_p and C_v) due to increase in temperature infers an increase in the thermal velocity of the atoms. Consequently, the thermal velocity of the atoms decreases with a decrease in pressure which affects C_p and C_v, respectively. In addition, the Gibbs free energy slope increased at a little rate at constant pressure. These novel results possessing improved thermostructural properties could be useful for high-temperature fatigue-resistant applications specially in a gas turbine engine.