基于可控路径加载的金属熔化线研究

Phase transition of materials under extreme high temperature and high pressure is of particular importance for shock wave, materials and Earth science, etc. However, the melting curve of metals have been investigated experimentally through both static and shock techniques, but to date, a consensus is still lacking, even for the theoretical calculations. Recently, study on rate-dependence of polycrystalline transition and controlled-loading technology for metals provide valuable information regarding the transition kinetics, so it may worth us to take some effort on melting of metals in the same way. So, in this proposal, bismuth with low melting point, large amount of static and shock experiment data, is engaged as the representative metal, and a controlled-path loading technique with various rate is employed here for phase transition, which may cross the melting curve. Together with numerical simulation, evidence for phase transition may be obtained with kinds of thermodynamics parameters detected in our work, whose strain rate stay between static and shock experiments. We hope this project would offer us benefit information on melting curve of metal subjected to controlled-path loading resolidification, and provide a reliable basis for phase transition model and theoretical investigation on melting.

极端高温高压条件下材料的相变行为一直是冲击波物理、材料科学、地球物理等关注的重点。然而，金属材料动-静压熔化线差异的问题历经了数十年的研究，争议颇多，迄今为止却没有明确的理论模型和实验数据能够解释其中的原委。近年来，固-固相变率相关的研究结果和可控路径加载技术的实现使得金属材料动-静压熔化线差异问题的解决显得有迹可循。因此，本项目拟以熔点低、动-静压实验数据丰富的金属铋作为研究对象，采用初始冲击压缩的方式实现其熔化，随后利用一种路径可控的加载技术实现对实验应变率的调控，并最终实现铋材料跨越固-液熔化线的相变，通过对该过程热力学物性参数的精确测量，结合数值模拟计算，获取其在熔化线附近、传统动-静压加载应变率范围之间相变的直接证据，在此基础上认识可控路径加载下应变率差异与动-静压实验结果差异之间的规律，为熔化相变模型和相变理论研究提供重要的实验数据。

极端高温高压条件下材料的相变行为一直是冲击波物理、材料科学、地球物理等关注的重点。近年来，固-固相变率相关的研究结果和可控路径加载技术的实现使得金属材料动-静压熔化线差异问题的解决显得有迹可循。本项目以熔点低、动-静压实验数据丰富的金属铋作为研究对象，采用初始冲击压缩的方式实现其熔化（首次冲击压力大于~28GPa），随后利用一种路径可控的阻抗梯度飞片加载技术实现对实验应变率的调控（10^5~10^6/s），并最终通过冲击加载-准等熵再加载实现铋材料跨越固-液熔化线的相变。基于位移干涉仪（DPS），通过对该过程样品/窗口界面粒子速度剖面等热力学物性参数的精确测量，结合数值模拟计算，获得其在熔化线附近、传统动-静压加载应变率范围之间相变的直接证据，为熔化相变模型和相变理论研究提供重要的实验数据。