退火对(Nd,Pr)12.8Dy0.2Fe77.4Co4.0B5.6快淬薄带晶化行为的影响

Effects of Annealing on Crystallization Characteristics of (Nd,Pr)_(12.8)Dy_(0.2)Fe_(77.4)Co_(4.0)B_(5.6) Ribbons

采用高真空高纯氩DSC测量了（Nd,Pr）12.8Dy0.2Fe77.4Co4.0B5.6非晶快淬薄带以及不同温度退火薄带的连续加热曲线,计算了晶化激活能、频率因子、晶化体积分数、晶化速率,研究了预退火前后薄带的晶化动力学和晶化过程。结果表明（Nd,Pr）12.8Dy0.2Fe77.4Co4.0B5.6快淬薄带在30 K/min加热速度时DSC曲线起始晶化温度865.8 K、峰值晶化温度877.2 K、晶化结束温度901.7 K,居里温度转折点581.2 K,富稀土相的初始熔化点1003.6 K。在高于峰值晶化温度或晶化结束温度退火10 min的薄带非晶完全晶化,居里温度处形成吸热峰,而低于803.0 K退火处理的薄带以及快淬薄带在相近温度处只有DSC转折点。相对于快淬薄带直接晶化的特征,在低于起始晶化温度的693.0~743.0 K退火处理的薄带晶化峰形相近;803.0 K退火处理后薄带的晶化峰的温度范围增宽：在10~40 K/min相同加热速度下其起始晶化温度均降低1.4%,晶化结束温度在加热速度20~40 K/min时达到、甚至高于快淬薄带直接晶化结束温度;在低于快淬薄带直接晶化的峰值晶化温度之前存在一个具有相同晶化速率的临界温度,在低于该临界温度时,退火薄带比快淬薄带具有较高的晶化速率、更不稳定;而在高于该临界温度,退火薄带比快淬薄带具有较低的晶化速率。

The DSC heating curves of（Nd,Pr）12.8Dy0.2Fe77.4Co4.0B5.6ribbons before and after annealing were measured under the conditions of first pumping high vacuum and then filling with high pure argon. The crystallization activation energy, the frequency factor, crystallization fraction, and crystallization rate were calculated, and the crystallization kinetics and process were studied. The results show that the initial crystallization temperature, the peak one, the final one, the curie temperature of the ribbons and the melting point of RE-rich are 865.8, 877.2, 901.7, 581.2 and 1003.6 K, respectively at the heating speed of 30 K/min. If the annealing temperature is higher than the peak crystallization temperature or the final one, the endothermic peaks of the ribbons after the annealing for 10 min, form at the curie temperature. And no obvious peaks appear on the DSC curves if the annealing temperature is not above 803.0 K. When the temperature is within the scope of 693.0-743.0 K, the crystallization peak shape of the ribbons after the annealing is similar to that of the ribbons before it. But the temperature scope of the peak is broadened when the annealing temperature is at 803.0 K. And all the initial crystallization temperatures of the ribbons after annealing at 803.0 K are decreased by 1.4% compared to those of the ones before the annealing on the DSC curves at the same heating speed from 10 K/min to 40 K/min, and the final temperatures are equal to or above those before the annealing. There is a critical temperature on DSC curves of the ribbons before and after the annealing at the same heating rate, where their crystallization rates are the same. If the crystallization temperature is lower than it, the crystallization rate of the ribbon after the annealing is higher than that of the one before the annealing, and the ribbon after annealing is more unstable. And if the crystallization temperature is above it, the crystallization rate of the ribbon after the annealing is lower than that of the ribbon before the annealing.