Effect of annealing treatment on formation of intermetallic phase in cold-sprayed Ni/Ti mechanical alloying coating

Three kinds of Ni/Ti mechanical alloying powder prepared by mechanical alloying at different milling time are employed to form Ni/Ti coatings by cold spraying. The microstructures of the coatings annealing under different conditions are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It is found that the formation temperature of Ni-Ti intermetallics from the cold-sprayed alloy is decreased with increasing ball milling time for powder preparation. Moreover, the phase constitutions change from Ni₃Ti, B2-NiTi and Ti₂Ni to Ni₃Ti and Ti₂Ni. The increase of annealing temperature only leads to the change of the relative content of different intermetallic phases in the coating. The results show that intermetallic B2-NiTi phase formed during annealing exhibits good stability during cooling process.