冲击波作用下钕铁硼的动态特性研究

The Dynamic Mechanical Properties of NdFeB Ferromagnet under Shock Wave Compression

为了研究钕铁硼铁磁性材料在冲击波作用下的力学与磁学性质,利用一级轻气炮驱动飞片的方法对钕铁硼进行冲击加载实验,采用锰铜压阻传感器测量了钕铁硼内部不同位置的压力变化历程。给出了3~7 GPa压力范围内,钕铁硼的Hugoniot关系以及冲击波阵面上压力与温度的关系;计算了钕铁硼的Grüneisen状态方程参数;建立了飞片碰撞加载钕铁硼的计算模型,对钕铁硼的冲击响应进行了数值模拟计算,计算得到的压力峰值与实验测得的压力峰值基本相符。对冲击后的磁体进行了微观结构观测,分析了钕铁硼退磁机制。结果发现:冲击后磁体发生沿晶断裂,磁体晶界相的微观结构没有发生变化,沿晶断裂弱化了晶界相隔断主相之间交换耦合的作用。经冲击的磁体的矫顽力损失很大,从21.4 k Oe降至3.2 k Oe,在难磁化方向矫顽力只有1.2 k Oe,但难易磁化方向并未发生改变。

In order to investigate the dynamic mechanical properties of Nd Fe B ferromagnet,the planar impact experiments are conducted by gas gun planar impact technique. The manganinpressure gauge is used to measure the pressure changes in Nd Fe B ferromagnet. The shock Hugoniot relation and the Grüneisen equation of state for Nd Fe B are obtained based on the analysis of the experimental data. The shock Hugoniot relation is described by the linear relation in the pressure range from 3. 3 GPa to7. 2 GPa,by which the parameters in the Grüneisen equation of state are determined. The shock pressure region is enough to make the magnet to be completely demagnetized according to the hysteresis loops. A two-dimension simulation model is established according to the planar impact experiment,and the numerical simulation is performed by the nonlinear dynamics method. In order to analyze the mechanism of shock demagnetization,the microstructure,crystal structure,and magnetic properties of the magnets are examined with scanning electronic microscope,X-ray diffractor,hysteresis loop measurement instrument,and vibrating sample magnetometer,respectively.