TEM study of structural and phase transformations in the Ni75Mo20Al5 alloy

Using the method of transmission electron microscopy, we studied the microstructure evolution of the Ni75Mo20Al5 alloy at temperatures ranging from 600 to 1600 °C. It has been shown that above the temperature of the transition “ordering-phase separation” (1200-1300 °C) a phase separation process occurs in the Ni/Mo and Ni/Al diffusion pairs. Below the transition temperature the Mo3Al and Ni3Al phases are formed. At temperatures of 800 °C and below, high-dispersion particles of the Ni3Mo phase precipitate. The role of Al in the heat resistance of Ni-Mo system superalloys is discussed.