准等熵压缩铁材料相变率相关特性研究

Study on the phase transition characteristic under dynamic loading is of great importance for high energy density physics, condensed matter physics, material science, defence engineering, industrial production, and so on. The quasi-isentropic compression has been accepted as a momentous way for the study of phase transition, as it could provide high and tuneable strain rate condition and at the same time lead to little temperature increase. At present the study on the strain-rate dependent characteristic of phase transition has become a research hotspot. However, its related micro-mechanism is still unclear. This project would focus on studying the strain-rate dependent characteristic of iron’s phase transition driven by laser quasi-isentropic compression. The laser quasi-isentropic loading technology with high and tuneable strain rate would be established, by optimizing the key parameters about the laser and the target structure. Meanwhile, a hybrid phase transition testing method would also be developed by combining the in-situ X-ray diffraction and the wave profile measurement technologies. Based on those efforts, the experimental platform could be constructed and a series of iron’s phase transition experiments will be performed on it with different strain rates. Then the collected experimental data will be analysed, so as to investigate the micro-mechanism behind the phase transition kinetics and phase transition process and further reveal the inherent law for the strain-rate dependent iron's phase transition phenomenon.

动载荷加载下材料相变特性研究，对于高能量密度物理、凝聚态物理、材料科学以及国防工程与工业生产等诸多领域具有重要的学术意义与应用价值。激光准等熵压缩，因其具备“应变率高且可灵活调控、压缩过程中温升较小”的独特性质，近年来已逐渐成为材料相变研究中一类非常重要的加载手段。材料相变的应变率特性是当前的研究热点之一，但其蕴含的微观机制尚不清晰。本项目将研究激光准等熵压缩铁相变的应变率特性。通过对加载光束及靶结构相关参数进行优化，建立应变率可调控的激光准等熵压缩技术。并将原位X射线衍射技术与波剖面测量技术相结合，建立宏微观相结合的相变联合诊断技术。在此基础上，开展一系列不同应变率条件下的准等熵压缩铁相变实验研究，获取相变过程中对应的X射线衍射图谱与速度波剖面数据。通过对上述实测数据进行反演，对相变动力学过程及相转变的微观机制进行深入研究，从而揭示铁相变应变率相关特性的内在规律。

准等熵加载下材料相变的应变率相关特性研究，近年来已成为研究者们持续关注的热点问题。对此进行更为深入的理论与实验研究，将有助于人们明确相变成核生长的微观机制，为相变过程建立更为清晰的物理图像。.项目开展了不同应变率条件下的单晶铁相变理论模拟与实验研究，建立了应变率可调控的准等熵加载技术及高时间分辨的动态X射线衍射诊断技术；自主研发了动态X射线衍射诊断包，成功实现了对单晶金属材料动态加载条件下动力学响应过程的动态X射线衍射诊断；开展完成了单晶铁样品相变过程的界面速度测量及动态X射线衍射诊断实验，获得了界面速度历史和高质量X射线衍射图谱数据；完成了单晶铁样品相变实验数据反演分析，通过分析揭示了单晶铁样品相边界随应变率变化的对数分布规律。.本项目的实施，对于研究者理解动态加载下材料相变的率响应特性具有重要意义。建立的动态X射线衍射和VISAR测速综合诊断测试技术还可为材料的其它动力学响应特性研究提供有力的技术支撑。