On iron contamination in mechanically alloyed Cr–Si powders

The present work reports on iron contamination and phase transformation during high-energy ball milling from high-purity elemental powder Cr–25Si, Cr–37.5Si, Cr–50Si, and Cr–66Si mixtures (at%) and their subsequent heat treatment. Samples were characterized in the as-milled state as well as after heat treatment by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microanalysis via energy dispersive spectrometry (EDS). Only Cr peaks were observed in Cr–25Si and Cr–37.5Si powders after milling for 200 h, suggesting that amorphous phases can be formed. In Cr–50Si and Cr–66Si powders, the CrSi and CrSi2 phases were formed during ball milling, respectively. In Cr–25Si and Cr–50Si milled powders, heat-treated at 1200 °C for 4 h, the formation of the Cr3Si and CrSi phases dissolving up to 15 and 16.9 at%Fe, respectively, was noted. In addition, the ternary Cr9Fe9Si2 phase was also formed in heat-treated Cr–25Si powders. A small amount of Cr5Si3 and CrSi2 was formed in heat-treated Cr–37.5Si and Cr–66Si powders, respectively.