DISORDERING OF THE NI3SI INTERMETALLIC COMPOUND BY MECHANICAL MILLING

The ordered f c c intermetallic compound Ni3Si was mechanically milled in a high-energy ball mill. The severe plastic deformation produced by milling induced transformations with increasing milling time as follows: ordered f c c --> disordered f c c --> nanocrystalline f c c. The structural and microstructural evolution with milling time was followed by X-ray diffraction, TEM, hardness tests, and differential scanning calorimetry (DSC). Complete disordering occurred at milling times of 2 h and kept the saturated DELTAH of the DSC peak in the range of estimated enthalpy even after 60 h milling. The structural development during milling of the f c c solid solution for Ni3Si was presumably dominated by the formation and refinement of a dislocation cell structure into microcrystallites which eventually reached nanometre dimensions.