Bi/MnBi eutectic in situ composite was produced by unidirectional solid-ification technique.The eutectic has a quasi-regular structure,in which the MnBi fi-bre is V-shaped in cross section and rod-like in longitudinal...Bi/MnBi eutectic in situ composite was produced by unidirectional solid-ification technique.The eutectic has a quasi-regular structure,in which the MnBi fi-bre is V-shaped in cross section and rod-like in longitudinal section,the aspect ratio isabout 300.The formation mechanism of this V-shaped MnBi phase was studied bycrystallographic analysis.The conclusion is that the(1120)face is the closest packedone while the(1010)face is the next.展开更多
Eutectic Bi/MnBi magnetic alloy was prepared by directional solidification.When the growth rate,R>2 cm/h,the MnBi fibre spacing,λ,distributed homogeneously in Bi matrix,follows λ~2R=constant.The thermal gradient....Eutectic Bi/MnBi magnetic alloy was prepared by directional solidification.When the growth rate,R>2 cm/h,the MnBi fibre spacing,λ,distributed homogeneously in Bi matrix,follows λ~2R=constant.The thermal gradient.G_L,does not influence λ.The magnetic property,B_r of Bi/MnBi alloy decreases with the increase of R and increases with the increase of G_L.展开更多
The solidification structure of Bi-3 wt pct Mn alloy grown up in the semisolid zone under the influence of a staticmagnetic field (up to 1.0 T) and the relation of the magnetic property with the solidification structu...The solidification structure of Bi-3 wt pct Mn alloy grown up in the semisolid zone under the influence of a staticmagnetic field (up to 1.0 T) and the relation of the magnetic property with the solidification structure have beeninvestigated experimentally. It was shown that the primary phase MnBi crystals in the alloy aligned and oriented alongthe direction of the applied magnetic field. The orientating tendency and the average length of the elongated MnBicrystals increased with the increase of the applied field and the solidification time. Moreover, the remanence of thealloy along the aligned direction of the MnBi phase in the case of solidification with a magnetic field was apparentlyanisotropic and nearly double of that without the magnetic field. This indicated that the MnBi crystals orientedand aligned along their easy magnetization axis. A model was proposed to explain the alignment and orientationgrowth of the MnBi crystals in a magnetic field in terms of the magnetic anisotropy of the crystals and the magneticinteraction between them.展开更多
During the solidification of Bi-Mn alloys from the mushy zone between 262 ℃ and 355 ℃ in a static magnetic field up to 1.0 T, the alignment behavior of the MnBi primary phase in the alloys was studied experimentally...During the solidification of Bi-Mn alloys from the mushy zone between 262 ℃ and 355 ℃ in a static magnetic field up to 1.0 T, the alignment behavior of the MnBi primary phase in the alloys was studied experimentally. The ferromagnetic MnBi crystals are magnetized and rotate their c-axes parallel to the field. Then, the oriented crystals congregate and grow up under the influence of magnetic interactions so that the alignment structure of the rod-like MnBi phase is produced. It is found that the orientation of MnBi crystals occurs immediately when the heating temperature or magnetic intensity reaches a critical value and beyond the value the orientation factor Γ of the MnBi phase is increased with increasing the heating temperature and the magnetic intensity. The critical temperature for Bi-6%Mn alloy is 275 ℃ in a 1.0 T magnetic field and increases to 290 ℃ when the magnetic field intensity decreases to 0.1 T. When the alloys are hold at 275 ℃, the critical magnetic intensity for Bi-6%Mn alloy is 0.4T and 0.05 T for Bi-3%Mn alloy. The orientation and congregation of the MnBi crystals were analyzed in terms of the magnetic anisotropy of the crystals and their magnetic interactions.展开更多
文摘Bi/MnBi eutectic in situ composite was produced by unidirectional solid-ification technique.The eutectic has a quasi-regular structure,in which the MnBi fi-bre is V-shaped in cross section and rod-like in longitudinal section,the aspect ratio isabout 300.The formation mechanism of this V-shaped MnBi phase was studied bycrystallographic analysis.The conclusion is that the(1120)face is the closest packedone while the(1010)face is the next.
文摘Eutectic Bi/MnBi magnetic alloy was prepared by directional solidification.When the growth rate,R>2 cm/h,the MnBi fibre spacing,λ,distributed homogeneously in Bi matrix,follows λ~2R=constant.The thermal gradient.G_L,does not influence λ.The magnetic property,B_r of Bi/MnBi alloy decreases with the increase of R and increases with the increase of G_L.
基金This work was supported by the National Natural Science Foundation of China(No.59871026,50225416,50234020)“Shu Guang”Shanghai Education Development Foundation(No.98SG37).
文摘The solidification structure of Bi-3 wt pct Mn alloy grown up in the semisolid zone under the influence of a staticmagnetic field (up to 1.0 T) and the relation of the magnetic property with the solidification structure have beeninvestigated experimentally. It was shown that the primary phase MnBi crystals in the alloy aligned and oriented alongthe direction of the applied magnetic field. The orientating tendency and the average length of the elongated MnBicrystals increased with the increase of the applied field and the solidification time. Moreover, the remanence of thealloy along the aligned direction of the MnBi phase in the case of solidification with a magnetic field was apparentlyanisotropic and nearly double of that without the magnetic field. This indicated that the MnBi crystals orientedand aligned along their easy magnetization axis. A model was proposed to explain the alignment and orientationgrowth of the MnBi crystals in a magnetic field in terms of the magnetic anisotropy of the crystals and the magneticinteraction between them.
文摘During the solidification of Bi-Mn alloys from the mushy zone between 262 ℃ and 355 ℃ in a static magnetic field up to 1.0 T, the alignment behavior of the MnBi primary phase in the alloys was studied experimentally. The ferromagnetic MnBi crystals are magnetized and rotate their c-axes parallel to the field. Then, the oriented crystals congregate and grow up under the influence of magnetic interactions so that the alignment structure of the rod-like MnBi phase is produced. It is found that the orientation of MnBi crystals occurs immediately when the heating temperature or magnetic intensity reaches a critical value and beyond the value the orientation factor Γ of the MnBi phase is increased with increasing the heating temperature and the magnetic intensity. The critical temperature for Bi-6%Mn alloy is 275 ℃ in a 1.0 T magnetic field and increases to 290 ℃ when the magnetic field intensity decreases to 0.1 T. When the alloys are hold at 275 ℃, the critical magnetic intensity for Bi-6%Mn alloy is 0.4T and 0.05 T for Bi-3%Mn alloy. The orientation and congregation of the MnBi crystals were analyzed in terms of the magnetic anisotropy of the crystals and their magnetic interactions.
