Liquid structure of Fe-1C-xSi alloy

The liquid structures of pure iron, Fe-1C, Fe-1Si at about 1550 degreesC and Fe-1C-xSi alloy in a range from melting point to 1560 degreesC were studied by high temperature X-ray diffractometer. Compared with the nearest neighbor distance r(1) =0. 259 nm and the first coordination number N-1 = 10.5 for pure liquid iron, there is a bigger r(1) and N-1 for Fe-1C alloy, but a smaller r(1) and N-1 for Fe-1Si alloy. There is a bigger decrease of r(1) for Fe-1C-1Si alloy than those of pure liquid iron and binary alloys. Cooling from 1560 degreesC to 1530 degreesC for Fe-1C-1Si alloy, an abrupt increase of N-1 from 10.3 to 11.8 exists in the liquid, which maintains at about 12.0 near the melting point. The existence forms for C and Si in binary liquids are different. In Fe-1C-1Si liquid, a phase transition of delta --> gamma exists in the temperature range from 1560 degreesC to 1530 degreesC, which extends to lower temperature range with increasing of Si content, and there is a single 6 phase existing in the melt at about 4%Si. The appearance of the phase transition is mainly caused by silicon atoms.