教育部【设备更新】岛津SEM-SERVO在纤维增强树脂基复合材料疲劳破坏研究中的应用

本文使用岛津SEM SERVO带扫描电子显微镜的高温原位疲劳试验机实时观察记录裂纹扩展长度，基于非线性弹性断裂力学通过公式计算材料的J积分，并转换为与J积分相对应的有效应力强度因子评价材料的断裂韧性。

Electrical contact materials are generally Ag- or Cu-based composites and play a critical role in ensuring the reliability and efficiency of electrical equipments and electronic instruments. The MAX phase ceramics display a unique combination of properties and may serve as an ideal reinforcement phase for electrical contact materials. The biological materials evolved in Nature generally exhibit 3-D interpenetrating-phase architectures, which may offer useful inspiration for the architectural design of electrical contact materials. Here, a series of bi-continuous Ag-Ti₃SiC₂ MAX phase composites with high ceramic contents exceeding 50 vol.% and having micron- and ultrafine-scaled 3-D interpenetrating-phase architectures, wherein both constituents were continuous and mutually interspersed, were exploited by pressureless infiltration of Ag melt into partially sintered Ti₃SiC₂ scaffolds. The mechanical and electrical properties as well as the friction and wear performance of the composites were investigated and revealed to be closely dependent on the ceramic contents and characteristic structural dimensions. The composites exhibited a good combination of properties with high hardness over 2.3 GPa, high flexural strength exceeding 530 MPa, decent fracture toughness over 10 MPa m^1/2, and good wear resistance with low wear rate at an order of 10^-5 mm³/(N·m), which were much superior compared to the counterparts made by powder metallurgy methods. In particular, the hardness, electrical conductivity, strength, and fracture toughness of the composites demonstrated a simultaneous improvement as the structure was refined from micron- to ultrafine-scales at equivalent ceramic contents. The good combination of properties along with the facile processing route makes the Ag-Ti₃SiC₂ 3-D interpenetrating-phase composites appealing for electrical contact applications.

电接触材料广泛应用于电气开关、功率继电器等电子电气设备，在开关电路、传导电流和承载等方面发挥着关键作用，对于保障电子仪器和电气设备的安全可靠与高效运行至关重要。电接触材料需要具有优异的导电性和导热性、良好的力学性能，以及高耐磨性和抗电弧侵蚀性能。常用的电接触材料通常是由导电金属铜或银与一种或多种增强相组成的复合材料，其中铜或银提供导电性和导热性，而增强相提供硬度、强度、耐磨性和抗电弧侵蚀性能。相比于铜基复合材料，银基电接触材料具有电导率和热导率高、接触电阻小、化学性质稳定等优点。商用银基电接触材料的增强相主要包括金属（如钨、镍、钛）和陶瓷（如氧化锡、氧化镉、氧化锌）两大类。MAX相陶瓷具有共价键、金属键、离子键等混合键合状态，兼具金属和陶瓷的优异特性，并且与银之间具有良好的润湿性，有望作为银基电接触材料的理想增强相。目前已报道的Ag-MAX相复合材料大多采用粉末冶金法（热压烧结或放电等离子烧结等）制备而成，材料中的MAX相分散在银基体中，难以避免孔洞、杂质等缺陷，并且材料的微观结构有待进一步优化控制，性能亟待提升。与之相比，自然界经长期进化形成的生物材料往往表现出微观三维互穿结构，各组元均保持连续并且在三维空间相互穿插，该结构被证实可有效保留组元的性能优势，并促进组元间应力传导，提升复合材料的损伤容限。生物材料的巧妙结构可为高性能Ag-MAX相电接触材料研制提供有益的启示。