The Effects Of W And Mo Addition On The Magnetic Properties,Phase Composition Of Co-Zr Based Alloys

In this paper, we have investigated the effects of W and Mo addition on the magnetic properties, phase composition and microstructure of Co-Zr based non rare earth permanent melt-spun ribbons. We have produced the sample of single phase Co5 Zr by the method of W and Mo addition and proved that the Co5 Zr phase is not a hard magnetic phase but a soft one. It is also proved that the addition of W and Mo could enhance the hard magnetic properties of Co-Zr based non rare earth permanent and we have investigated the source of coercivity increasing. It is mainly influenced by the microstructure and magnetocrystalline anisotropy field. What we have investigated is of great significance to handle the dispute that the hard magnetic phase of Co-Zr based al oys. It is helpful for the later research work of Co-Zr based non rare earth permanent.This paper has mainly two parts. First, the effects of W addition on the magnetic properties, phase composition and microstructure of Co-Zr based non rare earth permanent melt-spun ribbons. Second, the effects of Mo addition on the magnetic properties, phase composition of Co-Zr based non rare earth permanent melt-spun ribbons.Part one, Co-Zr-W alloy ingots were prepared by arc-melting and the melt-spun ribbons were successfully produced by rapidly quenched technology. And we discussed the magnetic properties, phase composition and microstructure of Co-Zr-W melt-spun ribbons detailedly. First, we studied the effect of W addition on the phase composition of Co-Zr based melt-spun ribbons. Under the requirement of a wheel speed of Vs=40 m/s, we produced a series of melt-spun ribbons Co82-x Zr18Wx(x=0,1,3,5,7,9)by rapidly quenched technology. X-ray diffraction(XRD) revealed that the addition of W is helpful for the formation of phase Co5 Zr. The sample x=0 consisted of the single phase Co11Zr2. With the increasing of x, we found that the phase Co11Zr2 decreased while the phase Co5 Zr increased. When x= 9, the samples are composed by the single phase Co5 Zr. From thermomagnetic analysis(TMA), we found that the phase Co5 Zr is not a hard magnetic phase but a soft one, its C urie temperature is below the room temperature. And we also discovered that either the phase Co11Zr2 or Co5 Zr, its C urie temperature decrease s with the increasing of W content. That can be attributed to the entry of W into the lattice of Co11Zr2 phase and Co5 Zr phase and results in the band change and then changes the C urie temperature. Second, we discussed the effect of W addition on magnetic properties of the series of Co82-x Zr18Wx(x=0,1,3,5,7,9)melt-spun ribbons. It is indicated that with the increasing of W content, saturation magnetization decreases linearly, but the coercivity increases at first, till a maximum value i Hc=4.5 k Oe for the sample x=3, then it decreases sharply. To the sample x=3, the decreasing of the hard magnetic phase Co11Zr2 is not favorable for the increasing of coercivity. Then we investigated the source of the increasing of coercivity. Based on SEM results, we can know that the addition of W could refine the microstructure of the melt-spun ribbons. The sample x=0 consists of flake- like grains and then transforms into particle- like grains for the sample x=3. Next, we studied the variation of magnetocrystalline anisotropy field Ha, and discovered that it increases because of the addition of W. Therefore, we can draw a conclusion that the increasing of coercivity is mainly influenced by microstructure and magnetocrystalline anisotropy field.Part two, in order to prove the phenomenon of W addition is not accidental, we investigated the effects of its congener element Mo addition on the magnetic properties, phase composition and microstructure of Co-Zr based non rare earth permanent melt-spun ribbons. In the same way, at the quenching rate of Vs=40 m/s, we produced a series of melt-spun ribbons Co5-x Zr Mox(x=0,0.1,0.2,0.4,0.5,0.52)by rapidly quenched technology. From x-ray diffraction(XRD) analysis of these alloy ribbons, we find that the sample x=0 composed single phase Co11Zr2, with the increasing of x content, the mount of phase Co5 Zr also increases, for the samples x=0.4,0.5 and 0.52, there is only single phase Co5 Zr could be found. After that, the magnetic properties were measured by a vibrating sample magnetometer(VSM). From it, we can find that for the samples x=0,0.1 and 0.2 put up hard magnetic property, then become weaker with the increasing of x content. When the x content is x=0.52, which sample consists single phase Co5 Zr, its magnetic property is very weak. Then, we discussed the effect of Mo addition on magnetic properties of the series of melt-spun ribbons Co5-x Zr Mox(x=0,0.1,0.2,0.4,0.5,0.52). It is indicated that with the increasing of x content, the saturation magnetization decreases all the time, but the coercivity increases in the beginning, till the optimal value i Hc=2.5 k Oe for the sample x=0.2, then it decreases sharply. After that, because of annealing could increase the sample’s magnetic property, so we suppose the phase Co5 Zr is a hard magnetic phase. Anneal the melt-spun ribbons x=0.2,0.4,0.52 at the temperature range of 500℃-700℃ spaced 50℃ apart. Then, we found that the sample x=0.2 at 600℃ reach the optimal value i Hc=4.9 k Oe. And for the sample x=0.52, the differences of the coercivity at different temperature are so little and all of them show paramagnetic. It is further evidence that the phase Co5 Zr is a soft magnetic phase. Co-Zr-Mo and Co-Zr-W melt-spun ribbons flow the same laws, it means that our work is correct and meaningful.