Synthesis of multiphase intermetallic compounds by mechanical alloying in Ni–Al–Ti system

In this paper, we based our investigations on the isothermal (900 °C) of the Ni-rich corner of the Ni–Al–Ti phase diagram and chose the compositions corresponding to the corners and inner of the tie-triangle of the equilibrium phase diagram to proceed high-energy ball milling. Nano-crystalline Ni(Al,Ti), Ni2AlTi and Ni3(Al,Ti) phases in the Ni–Al–Ti system were synthesized by mechanical alloying of elemental powders in a horizontal rotary ball mill. The crystallite size was the finest ∼7.5 nm when Ni(Al,Ti), Ni2AlTi and Ni3(Al,Ti) phases co-exist after prolonged milling. Formation kinetics was also analyzed using Johnson–Mehl–Avrami (JMA) equation. The Avrami exponent n is less than 2.5, which indicates that the reaction of solid solution formation is diffusion controlled. After annealing the milled powders at 1150 °C for 2 h and then at 900 °C for 100 h, the Ni(Al,Ti), Ni2AlTi and Ni3(Al,Ti) phases co-exist very clearly.