Mechanically Driven Solid State Amorphization Reaction of Fe_<50> W_<50> Alloy Powders

概要

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Equiatomic amorphous iron tungsten (Fe_<50>W_<50>) alloy powders have been synthesized by a low energy ball mill under purified argon atmosphere at room temperature. The mode of amorphization and crystallization of Fe_<50>W_<50> alloy powders have been investigated by means of X-ray diffraction, scanning electron microscopy and differential thermal analysis. The mechanical alloying process via ball-milling technique is classified into three stages of milling. At the first stage of milling, the elemental powders of Fe and W particles grow in size to form composite particles of larger diameter as a result of the cold welding. At the second stage of milling, elemental W powders diffuse completely into the Fe matrix to form bcc-FeW solid solution. Further milling creates mechanical deformations such as point and lattice defects that lead to raise the free energy of the solid solution to a less stable phase of amorphous Fe_<50>W_<50> alloy. During the last stage of milling, a homogeneous phase of amorphous Fe_<50>W_<50> alloy powder is formed. The end-product of the powder particles posses homogeneous smooth spherical shapes with an average size of about 0.5μm in diameter. The crystallization characteristics presented by the crystallization temperature, T_X, and the enthalpy change of crystallization, ΔH_X, are 850 K and -9 kJ/mol, respectively.Fe_<50>W_<50> alloymechanical alloyingamorphous phaseenthalpycrystallization
東北大学の論文
1996-03-28