磁驱动准等熵压缩下铁的相变

磁驱动准等熵加载技术是一种新型的可实现动态斜波压缩的实验技术,其加载路径介于准静态压缩(等温过程)和冲击压缩(绝热过程)之间,是联系这两种传统加载技术的桥梁.本文利用斜波加载技术完成了铁的准等熵压缩相变实验,研究了铁样品后表面声阻抗匹配对相变波形的影响;利用自由能为基础的多相物态方程方法对实验过程进行了模拟,数值模拟结果显示相变弛豫时间约30 ns,相变压力约13 GPa,计算与实验的界面速度历史基本重合;利用应力波理论对样品中的波系演化过程进行了分析,指出铁在相变混合区声速下降和窗口材料声阻抗是影响界面速度波形的主要因素.

Phase transition of iron under magnetically driven quasi-isentropic compression

The technique of magnetically driven quasi-isentropic compression is a new experimental technology which can generate dynamic ramp compression, and its load path lies between the quasi-static（isothermal） and shock compression（adiabatic process）, it is a bridge to contact the two traditional loading techniques. In this paper, the phase transition experiments of iron were done under magnetically driven quasi-isentropic compression technology on the facility CQ-4, and the effect of acoustic impedance on the interface velocity was analyzed. Simulation with multi-phase equation of state also was done to analyze the phase transition, and the simulations show that the phase transition relaxation time is about 30ns, and that the phase transition pressure is about 13 GPa, and that the numerical and experimental interface velocities are essentially coincident. With the analysis of evolution of the stress wave in the sample, it shows that the sound speed drop and the acoustic impedance of the window are the main factors to affect the interface velocity waveform.