The martensitic transformation for Co50Ni20Ga30 ribbon synthesized by the melt-spinning technique was studied by means of X-ray diffraction and ac magnetic susceptibility. The Co50Ni20Ga30 ribbon, having bcc phase wit...The martensitic transformation for Co50Ni20Ga30 ribbon synthesized by the melt-spinning technique was studied by means of X-ray diffraction and ac magnetic susceptibility. The Co50Ni20Ga30 ribbon, having bcc phase with calculated lattice parameters of a=0.57431 nm at 313 K. It exhibits a structure transition from parent phase to martensite during cooling. The martensitic phase in Co50Ni20Ga30 ribbon is tetragonal structure with lattice parameters of a=b=0.5422 nm and c=0.6401 nm. (c/a>1). According to the changing of diffraction intensity for martensite and the change of ac magnetic susceptibility, the process of the martensitic transformation can be divided into three parts during cooling from 283 K to 213 K. When the temperature decreasing sequentially from 193 K to 110 K, the structure of the martensite has a change in which the a-axis decreases and c-axis increases. The morphologies of selfaccommodation were observeds. The parallelogram morphology, the diamond morphology and the fork morphology were found.展开更多
The amorphization and magnetic properties of Fe_(62)Nb_(38) mechanicallyalloyed powders were investigated. In the initial mechanical alloying processes, the latticestructure of pure Fe is destroyed due to the cold-wel...The amorphization and magnetic properties of Fe_(62)Nb_(38) mechanicallyalloyed powders were investigated. In the initial mechanical alloying processes, the latticestructure of pure Fe is destroyed due to the cold-welding and fracturing, accompanying the reductionof ferromagnetic properties. The M_S value of Fe_(62)Nb_(38) powders with ball-milling time t = 6 his only 48.1 A·m^2/kg. With prolongating of mechanical alloying processes, a solid stateamorphization reaction (SSAR) takes place and the Fe-Nb ferromagnetic amorphous phase is formed.With the milling time increasing from 6 to 18 h, the saturation magnetization of Fe_(62)Nb_(38)powders increases with enhancement of the proportion of ferromagnetic amorphous phase in milledpowders. The M_S value of the Fe_(62)Nb_(38) amorphous powders is 98 A·m^2/kg, which is very closeto the value estimated from dilute model. However, the Curie temperature of the Fe_(62)Nb_(38)amorphous phase is only 206℃, which is much smaller than that of the pure Fe. This implies that theexchange interaction between Fe atoms in amorphous alloyed Fe_(62)Nb_(38) becomes weak due to theNb dilution. Investigation shows that the variation of magnetic properties of milled powders is oneof important tools for describing the amorphization by mechanical alloying.展开更多
基金This study was supported by the National Natural Science Foundation of China grant No.50271023 the Natural Science Foundation of Hebei Province(No.503031).
文摘The martensitic transformation for Co50Ni20Ga30 ribbon synthesized by the melt-spinning technique was studied by means of X-ray diffraction and ac magnetic susceptibility. The Co50Ni20Ga30 ribbon, having bcc phase with calculated lattice parameters of a=0.57431 nm at 313 K. It exhibits a structure transition from parent phase to martensite during cooling. The martensitic phase in Co50Ni20Ga30 ribbon is tetragonal structure with lattice parameters of a=b=0.5422 nm and c=0.6401 nm. (c/a>1). According to the changing of diffraction intensity for martensite and the change of ac magnetic susceptibility, the process of the martensitic transformation can be divided into three parts during cooling from 283 K to 213 K. When the temperature decreasing sequentially from 193 K to 110 K, the structure of the martensite has a change in which the a-axis decreases and c-axis increases. The morphologies of selfaccommodation were observeds. The parallelogram morphology, the diamond morphology and the fork morphology were found.
文摘The amorphization and magnetic properties of Fe_(62)Nb_(38) mechanicallyalloyed powders were investigated. In the initial mechanical alloying processes, the latticestructure of pure Fe is destroyed due to the cold-welding and fracturing, accompanying the reductionof ferromagnetic properties. The M_S value of Fe_(62)Nb_(38) powders with ball-milling time t = 6 his only 48.1 A·m^2/kg. With prolongating of mechanical alloying processes, a solid stateamorphization reaction (SSAR) takes place and the Fe-Nb ferromagnetic amorphous phase is formed.With the milling time increasing from 6 to 18 h, the saturation magnetization of Fe_(62)Nb_(38)powders increases with enhancement of the proportion of ferromagnetic amorphous phase in milledpowders. The M_S value of the Fe_(62)Nb_(38) amorphous powders is 98 A·m^2/kg, which is very closeto the value estimated from dilute model. However, the Curie temperature of the Fe_(62)Nb_(38)amorphous phase is only 206℃, which is much smaller than that of the pure Fe. This implies that theexchange interaction between Fe atoms in amorphous alloyed Fe_(62)Nb_(38) becomes weak due to theNb dilution. Investigation shows that the variation of magnetic properties of milled powders is oneof important tools for describing the amorphization by mechanical alloying.
