SUPERSATURATED A2 SOLID-SOLUTION INDUCED BY BALL-MILLING IN THE FE - SI SYSTEM - STRUCTURAL AND MAGNETIC CHARACTERIZATION AND THERMAL-STABILITY

Based on X-ray diffraction (XRD) pattern analysis and differential scanning calorimetry (DSC), we studied the far from equilibrium phase transitions induced by mechanical alloying (IMA) as well as the magnetic properties of Fe - Si samples with 33 and 37.6 at % Si. Two high ball milling (BM) shock powers are used in order to check the possibility of further expansion of the A2 crystalline disordered solid solution phase domain. For the two studied compositions, BM induces the formation of a mixture of the A2 crystalline disordered solid solution and an amorphous phase. The A2 phase grain sizes, the A2 lattice parameter, and the amorphous phase crystallization activation energy are 3 to 7 nm, 0.285 nm, and 160 to 270 kJ mole(-1) for the 33 at. % Si composition and from 3 to 7 nm, 0.284 nm, and 274 to 298 kJ mole(-1) for the 37.5 at. % Si composition. The influence of the structural state and the grain size on the coercive force are studied. A coercive force of 2.288 kA/m at 600 Hz and 0.145 T was found for the 37.5 at. % Si composition sample.