Morphology of ordering Fe-Si alloys

The microstructure of some Fe-Si alloys water-quenched from 700–1200°C and aged at 550–675°C for various times has been studied by means of transmission electron microscopy (TEM). It has been shown that at temperatures of 700°C and above the microstructure of the alloy is a solid solution with two-dimensional particles of a B2 ordered phase. These particles have a FeSi composition and lie along (100) planes of the matrix. At temperatures of 675°C and below a modulated microstructure is formed; in its enriched modulations the composition of the Fe₃Si phase is attained and D0₃ ordering occurs. Phase composition of some high-silicon alloys has been determined by X-ray diffraction phase analysis. It corresponds to + B2 or + D0₃. These results are plotted on the accepted Fe-Si phase diagram.