基于RUS方法的稳定各向同性负泊松比合金材料的研制及特性分析

Compared with positive Poisson's ratio materials, materials with negative Poisson's ratio have much higher shear modulus, fracture toughness, resistance to indentation and the energy absorption efficiency etc.; therefore, negative Poisson's ratio has attracted a growing interest from global researchers. Researchers are devoted to obtaining a deep understanding of the deformation mechanism of negative Poisson's ratio and developing a broad application of the materials and structures with negative Poisson's ratio. Until recently, negative Poisson's ratio has been observed in In-Sn alloy within a wide range of temperature by the applicant. There is no report about negative Poisson's ratio in isotropic solids until now. However, the mechanism and characterization of negative Poisson's ratio in this material is still under request. The project will systematically fabricate In-Sn alloys with a series of compositions in the vicinity of the morphotropic βSn+γ-γ phase boundary,and use different heat treatment methods to develop isotropic alloy materials with negative Poisson's ratio. Using advanced resonant ultrasound spectroscopy (RUS) method combined with the finite element software to determine the Poisson's ratio of the alloys.The sensitivities of the Poisson's ratio to the heat treatment histories and services environment will be studied combining with the microstructure analysis. This project will also determine the indentation resistance and the energy absorption capabilities of the alloys with negative Poisson's ratio, and compare the microstructures and mechanical properties of the alloys with negative Poisson's ratio with the materials which have transient negative Poisson's ratio during solid phase transformation such as barium titanate, etc..The results will provide the fundamentals for the design and fabrication of materials and structures with negative Poisson's ratio in the future.

负泊松比材料由于具有更高的剪切模量、断裂韧性、压痕阻力及吸能效率等传统材料无法比拟的优越性能，一经发现，立刻受到新材料领域的高度关注。而对负泊松比材料机理的研究及具有广泛应用价值负泊松比材料和结构的研制，一直是学者们关注的热点。申请人近期观测到各向同性铟锡合金在较宽温度区间内具有稳定的负泊松比行为，该行为之前未见报道，但其机理及特性还尚未明确。本课题拟通过在βSn+γ-γ准同型相界附近制备一系列不同成分比的铟锡合金，经不同的热处理过程，研制出各向同性负泊松比铟锡合金材料；通过超声共振谱方法(RUS)结合有限元仿真，确定出不同成分比铟锡合金准确的泊松比数值；结合材料的显微结构，分析负泊松比铟锡合金对热处理过程、服役环境的敏感度；对负泊松比铟锡合金进行压痕阻力及吸能效率测试，并与在固态相变时具有非稳定负泊松比行为的钛酸钡等材料的微观结构和力学性能进行对比，为今后负泊松比结构的人工制备奠定基础。

本项目圆满完成了《项目计划任务书》中规定的研究目标和研究任务，并超额完成了各项考核指标。负泊松比材料是一种具有更高剪切模量、断裂韧性、压痕阻力及吸能效率等优越性能的新材料。目前具有负泊松比现象的实体材料绝大多数是各向异性的，而本项目所研究的铟锡合金不但是各向同性的，且在特定的成分比下具有稳定的负泊松比行为。为进一步明确其机理及力学特性，本项目通过在βSn+γ-γ准同型相界附近制备一系列不同成分比的铟锡合金，经不同的热处理过程，研制出了各向同性负泊松比铟锡合金材料；通过超声共振谱方法(RUS)结合有限元仿真，得到了全范围泊松比(-1~0.5)与材料共振频率比之间的关系，进而确定出了不同成分比铟锡合金准确的泊松比数值；利用光学显微镜、X射线衍射（XRD）、透射电子显微镜（TEM）以及扫描电子显微镜（SEM）等手段分析了具有不同成分比的铟锡合金的微观组织，并结合材料的显微结构，分析了负泊松比铟锡合金对热处理过程、服役环境的敏感度；对负泊松比In-Sn合金进行压痕阻力及吸能效率测试，并结合显微组织结构，分析了负泊松比结构的变形机理，确定出了吸能效率最优的负泊松比In-Sn合金材料的参数值。主要研究成果包括：13.5%的铟锡合金具有负泊松比特性，泊松比可达到-0.09，且其负泊松比行为在所研究的温度变化范围内是稳定的；相比正泊松比InSn合金，负泊松比InSn合金具有更明显的应力平台区间，吸能效率更高；抗压痕能力方面正负泊松比的InSn合金没有明显区别。所得研究成果将为负泊松比材料和结构的人工制备及其在焊料、涂层、防护装置、宇航等众多领域的广泛应用奠定基础。本项目共发表学术论文10篇，其中SCI收录7篇，EI收录2篇（均标注本基金项目资助）；培养硕士研究生2名。