Phase transformations in powder iron-nickel alloys produced by mechanical alloying

Phase transformations in Fe-Ni alloys produced by mechanical alloying have been investigated by X-ray diffraction, Mossbauer spectroscopy, and magnetometric methods. The critical temperatures of phase transformations during heating and cooling of the alloys in the concentration range of 12-26 at % Ni have been determined, and the intervals of existence of phases at room temperature have been established. In the alloys that contain less than 16 at % Ni, a "normal" (diffusion-controlled) gamma-alpha transformation was observed. In some alloys, an isothermal gamma-alpha(2) martensitic transformation has been revealed, which was not earlier observed in cast Fe-Ni alloys. A considerable reduction in the start temperatures of the martensitic transformation in comparison with the cast alloys of the same nominal compositions has been found. Factors are considered that are responsible for the observed values of the temperatures of diffusionless transformations in the mechanically alloyed materials.