斜波压缩下锡的相变动力学特性

利用磁驱动加载装置(CQ-4)和高精度速度测试装置(DPV),开展了斜波加载下锡的动态压缩实验。实验结果表明:锡在加载阶段经历了弹塑性转变和相变等物理过程,相变压力约为7.5 GPa。β–γ相变对应的特征速度随着锡厚度的增加,从676.3 m/s减小到636.8 m/s,对应的压力从7.62 GPa降低到7.11 GPa。结合Hayes多相状态方程和非平衡相变动力学模型,对锡的斜波压缩实验过程进行了模拟,数值计算结果可以较好地描述锡在加载阶段的弹塑性转变和相变等物理过程。讨论了体模量在不同热力学过程中的物理形式,计算结果显示,斜波压缩过程需考虑压力对体模量的修正。分析了相变弛豫时间、体模量等典型物理参数对速度波形的影响,结果表明,相变弛豫时间和各相初始自由能主要影响混合区部分速度波形,γ相的体模量参数只影响相变后的速度波形,β相的体模量参数会影响整体速度波形。

Dynamic Characteristics of Phase Transition of Tin under Ramp Wave Loading

The dynamics of phase transition of tin under ramp wave loading was studied with experiment and simulation.The ramp wave compression experiment of tin was carried out with photonic Doppler velocimetry(PDV)and compact pulsed power generator CQ-4.The velocity wave profiles obtained experimentally show that tin undergoes physical processes such as elastoplastic transition and phase transition in the loading section,and the phase transition pressure is about 7.5 GPa.As the increase of thickness of tin,the characteristic velocity corresponding to the onset of phase transition decreased slightly from 676.3 m/s to 636.8 m/s,and the corresponding pressure was from 7.62 GPa to 7.11 GPa.The Hayes multi-phase equation of state and non-equilibrium phase transition kinetic model were employed to simulate the experimental process,and the numerical results can well describe the physical processes such as elastoplastic transformation and phase transformation in the loading section.The calculated results revealed that the correction of the bulk modulus with pressure needed to be considered under ramp wave compression.The influence of typical physical parameters,such as phase transition relaxation time and bulk modulus,on the velocity waveform was discussed.The results show that phase transition relaxation time and initial free energy mainly affect the velocity waveform in the mixing zone,the bulk modulus of the two phases affect the velocity waveform after phase transition and overall velocity waveform respectively.