The Study On Glass Forming Ability And Magnetic Mechanism Of The Re-fe-al Amorphous Alloy

The total output of rare earth in our country, which is rich in rare earth resources, is leading in the world. The products of rare earth are most low value-added and less depth processing products, so good economic benefit has not been obtained in our country. In 1996, Inoue and co-workers announced the development of Re60Fe30Al10(Re=Nd or Pr) BMG rods(1-12 mm diameter) with good hard magnetic property a t room temperature and good glass forming ability. The new field for the application of rare-earth based bulk amorphous alloys in the hard magnetic materials has been opened up due to its good formability and simple preparation process. But the application of the Nd60Fe30Al10 alloy is restricted due to the high cost of Nd. The thesis is trying to obtain the new BMG with better glass forming ability and good hard magnetic property at room temperature by the substitute Ce, which is cheaper, for Nd in the Nd60Fe30Al10 al oy.In this dissertation, vibrating sample magnetometer(VSM), differential scanning calorimeter(DSC), X-ray diffraction(XRD), scanning electron microscope(SEM) and high resolution transmission electron microscopy(HRTEM) had been employed. In order to obtain the alloy with better glass forming ability and good hard magnetic property at room temperature, the magnetic property, glass forming ability, phase composition and microstructure of the NdxCe60-xFe30Al10(x=60~25) alloys were investigated. The magnetic property, phase composition and microstructure of that alloy, comparing with the Nd60Fe30Al10 alloy, were investigated to discuss the hard magnetic mechanism of the alloy. Meanwhile, the hard magnetic mechanism of the Fe53Nd37Al10 ribbons with hard magnetic propery was also discussed, and the results were summarized as follows:(1)The Nd30Ce30Fe30Al10 alloy is found to have the best glass forming ability in the NdxCe60-xFe30Al10 alloys, which has better glass forming ability than the Nd60Fe30Al10 al oy, the classic components.(2)The saturation magnetization Ms, remanent magnetization Mr and coercivity Hci of the Nd30Ce30Fe30Al10 alloy are 16.30 Am2/kg、10.22 Am2/kg and 162.31 k A/m, respectively. Because the cheaper Ce is added into the Nd30Ce30Fe30Al10 alloy, a brighter future is provided for the application of the rare-earth based amorphous al oy with hard magnetic property.(3)The Nd30Ce30Fe30Al10 alloy is mainly composed of the amorphous phase, which contains the Nd-rich amorphous phase(Tc1 phase, related to the low temperature magnetic phase) and the Fe-rich amorphous phase(Tc2 phase, related to the high temperature magnetic phase). Ce mainly substitutes the Nd atom in the Tc1 phase, so the curie temperature of the Nd-rich amorphous phase is reduced obviously. Meanwhile, there are some Nd-rich clusters of 5-10 nm in diameter in the amorphous matrix.(4)The intensity of exchange coupling interactions and pinning effect in the Nd60Fe30Al10 al oy is stronger than that in the the Nd30Ce30Fe30Al10 al oy.(5)The saturation magnetization and remanent magnetization of the ribbons with the cooling rate of 40 m/s and 20 m/s have the similar values, but the coercivity Hci of them are significantly different. The size of the nano-sized clusters in the ribbons with the cooling rate of 40 m/s is less than 5 nm. However, the size of nanoclusters in the ribbons with the cooling rate of 20 m/s is 5-10 nm and there are more nanoclusters in the ribbons. The intensity of exchange coupling interactions and pinning effect in the ribbons with the cooling rate of 20 m/s is stronger than the intensity in the ribbons with the cooling rate of 40 m/s.(6)The size of the activation diameter Da of Nd30Ce30Fe30Al10 alloy, Nd60Fe30Al10 alloy and Fe53Nd37Al10 ribbons is equivalent to the distance among some adjacent clusters. In these amorphous alloys, interactive units are formed among the adjacent clusters, and then the interactions among the interactive units will affect the hard magnetic property.