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用扭摆法测量了含锰18.5％的铁锰合金的内耗,在正和反马氏体型相变温度范围内都观察到一个稳定的内耗峯。在降温时,正马氏体型相变区域内的内耗峯出现在100℃左右;在重新加热时,反马氏体型相变区域内的内耗峯出现在200℃左右。对于这两个变为稳定以后的内耗峯进行了系统的研究,它们的共同特征是: 1.内耗峯的位置与测量内耗所用的振动频率无关; 2.稳定内耗峯的高度,随着测量内耗所用的应变振幅的增大而显著地升高; 3.随着对于试样的加热和冷却循环次数的增加,内耗峯的位置离相变开始点的温度越远,而且内耗峯的高度也下降。 从以上的特点可以看出,内耗峯的位置与频率无关表示产生内耗的基本过程不是受热激活所控制的。此外,内耗与振幅有关这一现象进一步指出,产生内耗的机构不是一种滞弹性效应。电子衍衬金相观测已经指出,作为扩展位错的组成部分的堆垜层错可以作为马氏体型相变的核,因此,这种内耗现象可能是由于扩展位错的应力感生加宽和收缩所引起的。这种模型可以统一地解释在铁锰合金中所观察到的各种内耗现象。
The internal friction of the Fe-Mn alloy containing 18.5% manganese was measured by the twist-off method. A stable internal friction peak was observed in both the positive and the anti-martensitic transformation temperature range. When cooling down, the internal friction peak in the positive martensitic transformation appears at about 100 ℃. When reheating, the internal friction peak in the anti-martensitic transformation appears at about 200 ℃. The two internal friction peaks, which have become stable, have been systematically studied. Their common features are: 1. The position of the internal friction peak has nothing to do with the vibration frequency used to measure the internal friction. 2. The height of the internal friction peak stabilizes. As the internal friction The strain amplitude used increases significantly and increases significantly; 3. As the number of heating and cooling cycles for the sample increases, the location of the internal friction peak farther from the onset of the phase change and the height of the internal friction peak also decrease . It can be seen from the above characteristics, the position of the internal friction peak has nothing to do with the frequency that the basic process of generating internal friction is not controlled by thermal activation. In addition, the correlation between internal friction and amplitude further points out that the mechanism that generates internal friction is not an anechoic effect. Electron diffraction metallography has pointed out that the stacking faults, which are part of the extended dislocation, can act as nuclei for the martensitic transformation. Therefore, the internal friction may be due to the stress induced broadening of extended dislocations and Shrinkage caused by. This model can uniformly explain the various internal friction phenomena observed in Fe-Mn alloys.