Enthalpy of Formation in the Al-Ni-Ti System

The Al-Ni-Ti ternary system forms the basis of several alloy systems of practical importance. This study was undertaken to provide additional experimental thermodynamic data for the modeling of the Al-Ni-Ti system. High-temperature direct reaction calorimetry has been used to determine the standard enthalpy of formation of several Al-Ni-Ti alloys. The stability of the L2₁ structure over the B2 structure at the stoichiometric composition of Ni_0.5Al_0.25Ti_0.25 was estimated from the enthalpy results to be 6.8 kJ/mol. The lattice parameters and melting temperatures of these compounds are also reported.