The sequence of phase formation during mechanical alloying of chromium and silicon powders

The sequence of phase formation during mechanical alloying of chromium and silicon powders has been studied using high-energy ball milling of mixtures of elemental powders with different Si/Cr atomic ratios. X-ray diffactometry and transmission electron microscopy have been utilized to identify the phases and to characterize the microstructure of the powders. All four equilibrium phases in the Cr-Si system can form. With a Si/Cr atomic ratio equal to or higher than 3/5, CrSi₂ is always the first phase to form, and then CrSi₂ can react with chromium to form CrSi or Cr₅Si₃, depending on the Si/Cr atomic ratio. This is similar to the sequence of phase formation during annealing of multilayer chromium and silicon thin films. However, with low Si/Cr atomic ratio close to 1/3, Cr₃Si is the first and only phase to form during mechanical alloying.