Measurements of high phase transition temperatures and construction of Ni-Si-Zr phase diagram

Abstract

There is a hindrance in modeling Gibbs energies of high melting alloys via the CALPHAD approach because of the scarcity of experimental results. All the conventional methods suffer to overcome the practical difficulties at high temperatures. Despite these setbacks, this paper provides a reliable way of using an arc-melting device in conjunction with a pyrometer to measure high-temperature phase transitions and developing a hybrid approach to construct a Ni-Si-Zr phase diagram. First, the preparation of Ni-Si-Zr alloy is via arc-melting technique. Forty-two as-cast sample analyses provide the primary solidifying phase encompassing the Ni-Si-Zr composition domain. Heat-treatment of fifteen samples at 1073 K refines the isothermal section, emphasizing the Zr-rich corner. Ni-Si-Zr alloy’s temperature recording using pyrometer in the arc-melting device while cooling after melting reveals novel Ni-Si-Zr’s invariant reactions. The time versus temperature graph comparison with its as-cast electron micrograph reveals several phase transitions. The notable research output of this research work is the hybrid approach, including the experiments circumventing hurdles at high temperatures and the first-principles method to calculate the intermetallic phase’s formation energy. The hybrid approach in the present work has established a phase diagram and the thermodynamic description over the extensive temperature and composition ranges for a highly complicated ternary system. The presently developed hybrid methodology is also applicable to construct a phase diagram for other complex ternary systems up to ≈ 3700 K.