面向高温、高压、高应变速率极端条件钨/钢梯度界面设计及界面孪晶变形机理研究

Tungsten/steel composite material is one of the most promising structural materials for applications in extreme conditions such as high temperature, high pressure, and high strain rate. Unfortunately, the design of tungsten/steel composite structure, at current stage, is mainly based on quasi-static physical properties, without consideration of the special requirement of extreme conditions. In view of this issue, we target on the rational design of tungsten/steel graded interface by combining the quasi-static physical properties and dynamic properties at extreme conditions, specifically, the newly observed twinning deformation at high temperature, high pressure, and high strain rate. In this project, we will first calculate the quasi-static physical properties of tungsten/steel alloys in the whole concentration range using first principles calculation. Then, we will study the twinning behavior on the tungsten/steel interface by means of molecular dynamics simulation and, more importantly, find out the optimum interface structure which can block the movement of twinning under extreme conditions. By integrating the quasi-static physical properties from first principles calculation and the dynamic properties from molecular dynamics simulation, we will perform a combinatorial optimization on the tungsten/steel graded interface properties through a simulated annealing algorithm. The rational design of tungsten/steel graded interface will yield an optimum tungsten/steel graded material with strong interface bond and the resistance of twinning deformation. In addition, our findings not only help us design and utilize tungsten/steel composite material, but also shed lights on the understanding of mechanical behavior of materials under extreme conditions.

钨/钢梯度材料是高温、高压、高应变速率等极端服役环境下极有潜力的结构材料，然而现有梯度界面设计仅考虑了准静态下的材料性能，而没有针对到极端条件这一特定环境。因此，本项目针对高温、高压、高应变速率下材料出现的孪晶变形行为，综合极端条件下动态响应规律和准静态下材料性能进行钨/钢梯度界面设计。我们将通过分子动力学模拟研究界面对孪晶变形的作用机理，找出能够阻碍极端条件下孪晶变形的关键因素，结合准静态下第一性原理梯度层关键性能参数，利用计算机模拟退火算法组合优化梯度界面性能，设计出具有稳定界面结合、能够抵抗孪晶变形的钨/钢梯度界面结构，提升我们对材料在极端条件下响应行为基本科学问题的认识，为新型钨/钢梯度复合材料的研制和推广提供理论指导。

钨/钢复合材料是高温、高压、高应变速率等极端服役环境下极有潜力的新材料。然而钨与钢之间性能差异巨大，导致界面上易存在残余应力和热应力，影响材料的寿命和应用，甚至直接导致构件失效。本项目通过第一性原理计算和分子动力学模拟，结合关键实验验证系统研究了准静态下钨/钢界面结合的关键物理性能，动态加载下复合材料的力学响应行为。在此基础上，综合准静态下材料关键性能与极端条件下界面响应规律，实现钨/钢梯度界面设计。结果表明：1. 短程有序程度和原子排布的中心对称参数是决定钨钢复合材料力学性能的关键因素；2.界面晶体学位向决定了钨/钢界面的稳定性和力学响应行为，部分对称倾斜界面具有比外延界面更好的界面结合；3.界面动态力学行为主要发生在钨侧，钨的变形机制取决于加载方式，并随应变率升高发生转变；4.界面反应受晶体化学对称关系限制，导致贫碳和富碳环境下的反应产物截然不同。项目不仅实现了钨/钢梯度界面的可靠设计，也提升我们对界面在极端条件下响应行为基本科学问题的认识，为新型钨/钢梯度复合材料的研制和推广提供理论指导。

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