Investigation on Phase Evolution in Mechanically Alloyed Nano-Structured Fe-Si System

Abstract

In the present research, nano-crystalline Fe­70Si30alloy powders were prepared by mechanical alloying using Fe and Si powder as starting materials. Powder samples were taken from the mill at selected time intervals (5, 20, 40, 50, 60, 70h) for the structural properties analysis. The phase composition, morphology and magnetic properties of nano-structured alloy powders were analyzed by XRD, FESEM and VSM techniques, respectively. The evolution of non-equilibrium solid solution Fe (Si) during milling was accompanied by refinement of crystallite size. Dissolution of Si atoms into Fe matrix was also studied. The quantitative analysis of phase composition was carried out using Maud software which is based on the Rietveld method combined with Fourier analysis. XRD results showed a coexistence of BCC, DO3and FeSi structural phases for 40h milled sample, quantity of DO3and FeSi phases decreased for prolonged milling time. These phases disappeared in 60h milled sample and BCC FeSi phase with a mean crystallite and particle sizes of 20 and 70 nm were formed. The results also indicated that by mechanical alloying of the FeSi system for 60h, it was possible to extend the solubility of the BCC FeSi structure to 30 at% Si.