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本文用电阻、磁性测量和金相的方法研究了液相烧结 SmCo_5永磁体在850℃至室温范围内的组织变化。我们用电阻随温度的变化关系发现在750℃存在两个组织变化过程。一个是快速的,一般只在几分钟到几十分钟内完成,它是750℃左右时 jHc 急剧变坏的主要原因。在我们所用样品的条件下,析出物为2—17相,它是由组织的不平衡造成的。另一个组织变化是具有很长孕育期的(约4小时),速度极其缓慢的过程。从这种特征看,类似 Buachow 等人的所谓共析分解过程。该转变的动力学特征除上述外,转变是分级的。在约20小时的保温中没有看到明显的组织变化。我们的实验表明,它不是通常热处理中使 jHc 下降的原因。因此,我们证明了所谓共析分解是 jHc 在750℃急剧变坏的原因这一说法是不正确的。对100℃至650℃温度范围内电阻随温度时间的变化的研究,使我们发现低温下也存在组织变化和类似于通常的合金时效现象。这一组织变化的存在可能就是 SmCo_5永磁体在使用时,为了提高时间稳定性在较高的温度下事先短时间予处理的原因。鉴于 SmCo_5合金的工艺稳定性和时效稳定性的重要意义,对其组织变化的研究还需深入进行。
In this paper, the microstructures of liquid-phase sintered SmCo_5 permanent magnets in the range of 850 ℃ to room temperature were studied by means of electrical resistance measurement, magnetic measurement and metallography. We found that there are two histochemical changes at 750 ° C using the relationship between resistance and temperature. One is fast, usually only a few minutes to dozens of minutes to complete, it is about 750 ℃ when jHc sharp deterioration of the main reason. Under the conditions we use for the samples, the precipitates are in the 2-17 phase, which is caused by the imbalance of the tissue. Another organizational change is the process of very long gestation (about 4 hours), extremely slow. From this characteristic, the so-called eutectoid decomposition process similar to Buachow et al. In addition to the above dynamics of the transformation, the transition is graded. No significant tissue changes were seen in the incubation for about 20 hours. Our experiments show that it is not the cause of jHc decay in the usual heat treatment. Therefore, we prove that the so-called eutectoid decomposition is the reason why jHc abruptly deteriorates at 750 ℃. A study of the resistance versus temperature over the temperature range of 100 ° C to 650 ° C has led to the discovery that there are also tissue changes at low temperatures and similar to the usual alloy aging. The existence of this organizational change may be the reason why the SmCo_5 permanent magnet is pre-treated at a relatively high temperature in order to improve the time stability. In view of the process stability and aging stability of SmCo_5 alloy, the research of its structure needs further study.