面向宽温域、高能量吸收、大回复应变合金的耦合畴结构设计与性能优化

火星探测软着陆系统及车轮要求材料具有宽温域、高吸能、大回复应变的特性；形状记忆合金的超弹性满足高吸能、大回复应变的温度区间有限；虽然应变玻璃的超弹性温域宽，但吸能少、回复应变小。本项目提出构建由缺陷畸变场形成的多级应变网络，使得短程-长程马氏体畴产生强烈的耦合，达到在不降低应变玻璃宽温域特性的同时，获得长程马氏体畴的高吸能和大回复应变特性。本项目拟结合计算模拟、理论建模与实验，提出渗滤的应变网络应该是应变玻璃形成的微观机制，其宽温域超弹性应该来源于宽温域内存在的刚性应变网络，以建立多级应变网络形成的统一判据；据此构建描述由多级应变网络产生的短程-长程马氏体畴耦合结构的相场模型，阐明短程-长程马氏体畴之间的耦合机制，优化出最佳微观结构；进而实验设计与研制满足火星探测需求的新型合金。本项目的研究将有助于加深应变不均匀性对材料相变及力学行为影响机制的理解，同时为新型多功能合金的开发提供新思路。

The soft landing system for Mars exploration and its superelastic tire require materials showing high energy absorption and large recoverable strain in a wide temperature range. The superelasticity of conventional shape memory alloys can show the high energy absorption and large recoverable strain, but in a very limited temperature range; while the superelasticity of strain glass alloys occurs in a rather wide temperature range, but shows low energy absorption and small recoverable strain. In this project, a hierachical strain network formed by defect distortion field is proposed to make short-range and long-range martensite domains strongly coupled, so that the characteristics of high energy absorption and large recoverable strain of long-range martensite domains can be maintained without reducing the wide temperature range characteristics of strain glass. .Combined with computational simulation, theoretical modeling and experiments, it is proposed that the possible mechanism of strain glass formation is the percolation of strain network. The wide-temperature superelasticity originates from the rigid strain network existing in the wide-temperature range, and a unified criterion for the formation of the hierachical strain network is established. Based on this idea, a phase field model describing the coupling structure between the short-range and long-range martensitic domains generated by the hierachical strain network will be established and clarified. Corresponding to the best mechanical properties, the optimal microstructural characteristics were predicted, and new type of alloys showing both high energy absorption and large recoverable strain in a wide temperature range will be designed and developed to meet the requirements of the soft landing system for Mars exploration. This project will help to deepen the understanding of the effect of strain inhomogeneity on the phase transformation and mechanical behavior of shape memory alloys, and also provide a novel idea for the development of new multifunctional alloys.