镍在交变磁场中的一个磁内耗峰

在铁磁性物质中,弹性现象与磁性现象之间的耦合每每引起内耗。过去作磁弹性内耗研究所用的磁场大都是静磁场。我们令镍试样在交变磁场中作扭转振动,测量内耗。把内耗表示为磁场强度的函数时,得到一个显著的内耗峰。这个内耗峰在静磁场下不出现。把镍试样经过冷加工处理或在试样中加碳,都足以把内耗峰的位置移向高磁场强度的一边,而保温退火则把内耗峰移向低磁场强度的一边。此外,这个内耗峰的高度由于所用扭转频率的增加而显著地增加。根据镍的磁化曲线上各部分所相当的可逆及不可逆过程,可以定性地解释上述内耗峰的来源及其所受各种因素的影响。

A MAGNETIC INTERNAL FRICTION PEAK IN NICKEL UNDER ALTERNATING MAGNETIC FIELD

The coupling between elastic and magnetic phenomena in ferro-magnetic materials often gives rise to internal friction. In previous studies on magnetoelastic internal frictions, the applied magnetic field was mostly static. In the present experiment, nickel specimen was made to vibrate in torsion under an alternating magnetic field, and a pronounced internal friction peak was observed when internal friction was plotted as a function of the alternating magnetic field strength. This peak did not appear under similar conditions when using a static magnetic field. The position of the peak was shifted toward the side of a higher magnetic field when the nickel specimen was either cold-worked or contained carbon; and it was shifted toward the side of a lower magnetic field when the specimen was previously annealed at an elevated temperature. The height of the peak was considerably raised with an increase of vibrating frequency.A qualitative explanation of this peak is given on the basis of reversible and irreversible processes occuring at different stages of the magnetization curve of nickel. Factors affecting this peak arc discussed.