磁驱动飞片加载下纯铁的冲击相变和层裂特性

Shock-Induced Phase Transition and Spallation in Pure Iron under Magnetically Driven Flyer Plate Loading

使用磁驱动装置CQ-4发射紫铜飞片对纯铁样品进行一维平面应变加载,采用高精度激光位移干涉仪(DPS)记录飞片和样品的自由面速度历史。结果显示,当纯铁样品在加、卸载过程中有αε相变发生时,样品的层裂强度达到3.4GPa,比已报道的未发生相变的纯铁的层裂强度(1.2~1.9GPa)有明显提高,其原因可能是纯铁材料在经历αε可逆相变时,内部晶格产生了大量的位错。通过分析样品的自由面速度历史,判断出样品发生了自由面浅表层裂现象。在对飞片和样品中的应力波系进行分析时,若只考虑塑性波和相变波在界面的反射稀疏波与飞片传入样品靶中的稀疏波之间的相互作用,将无法解释实验观测到的自由面浅表层裂现象,因此该现象可能与纯铁样品在逆相变过程中产生稀疏冲击波有关。

The magnetically driven device CQ-4 was used to drive a copper flyer plate to impact a pure iron specimen to achieve one dimensional plane-wave loading,and a high-accurate Doppler pin system was utilized to record the free-surface velocity histories of the flyer and specimen. The results indicate that if the pure iron material experiences a←→Е phase transition during shock loading and unloading,its spallation strength reaches to 3. 4 GPa which is distinctly higher than the reported value of 1. 2- 1.9 GPa without phase transition. The possible cause of this phenomenon is that a multitude of dislo- cations in the crystal lattices of the pure iron are formed during the a^--~e reversible phase transition. Moreover,the free-surface velocity history reveals that the spallation has occurred in the near-surface of the specimen. The formation of the shallow spallation may be related to the rarefaction wave formed at the time of reversal phase transition in the pure iron specimen. Because if only consider the interac- tions between the rarefaction waves generated by the reflection of plastic wave as well as phase transi- tion wave and rarefaction wave when analyzing the stress wave propagations in the flyer-specimen system,it is impossible to interpret the detected shallow spallation in the experiment.