The Research On Processes And Magnetic Properties Of Nd₂ Fe₁₄ B/α-Fe Nanocrystalline Melt-spun Ribbons

Nanocrystalline two-phase rare-earth permanent magnets are comprised of hard and soft magnetic phases, high magnetocrystalline anisotropy and high saturation magnetization are provided by them respectively. It has the excellent magnetic properties due to exchange-coupling interaction, and already accepted by world markets because of the merit of low rare earth content and high chemical stability. Nowadays, its application field is expanding gradually.In this paper, Nd₂Fe₁₄B/α-Fe nanocrystalline permanent magnetic ribbons were prepared by melt-spun and annealing processes. The phase component and magnetic properties of the ribbons with different composition, speed and annealing temperature were studied by means of XRD, DSC and VSM.Furthermore, ribbon's hysteresis loops nonlinear fitting were also studied. Melt-spun speed can influence the ribbon's crystallizing and magnetic properties significantly. The sample under optimal speed has single-phase characteristic. Two-phase characteristic will appear if melt-spun speed is below or above optimal speed. In addition, annealing temperature is an important factor to riboon's phase component and magnetic properties. When the temperature is about 730℃, the optimal magnetic property of S1 and S2 alloy ribbons can be obtained. When the temperature is more or less than 730℃, the ribbons'property will decrease.Compared with Nd-Fe-B ternary alloy, remanence and maximum energy product of quinary alloy which acquired by adding Dy, Co and Ga to Nd-Fe-B, are increased by 36.16% and 51.15% respectively.By comparising magnetic properties of ribbons with different composition, speed, measured and annealed temperature. The optimal magnetic property of Nd-Dy-Fe-Co-B-Ga alloy quenched at 35m/s can be obtained at 150K: M_r= 10.51kGs; Hci=9.07kOe; (BH)max=15.44MGOe; M_r/Ms=0.75. By means of hysteresis loops nonlinear fitting, seven-order polynomial is confirmed as the best one with goodness of fit and minimum error. It also faciliate other calculation procedure.