Enthalpy of formation of intermetallic phases from Al-Ni and Al-Ni-Ti systems

摘要

The formation enthalpy of binary AlNi and AlNi_3 and ternary Al_2NiTi, AlNiTi and AlNi_2Ti intermetallic phases was determined by the solution calorimetric method. The phases were prepared by the levitation technique and by melting metals in a glove-box operating with high purity argon. After the preparation, all phases were identified by X-ray diffraction (XRD) and the quantitative analysis was performed by means of a scanning electron microscope (SEM EDS). The formation enthalpies measured at room temperature for the binary and ternary phases are as follows: -66.3 ± 1.7 kj/mole of atoms for AINi, -40.5 ± 1.6 kj/mole of atoms for AlNi_3, -40.7 ± 1.8 kj/mole of atoms for Al_2NiTi, -56.9 ± 1.1 kj/mol of atoms for AINiTi and -72.1 ± 1.2 kj/mole of atoms for AlNi_2Ti.Additionally, for the AlNiTi phase, the measurements were conducted at the temperature of 1133 K and the determined formation enthalpy was found to equal -56.5 ± 2 kj/mol of atoms. The very near values obtained at room and elevated temperature point to the fact that it is independent of temperature.