나노인덴테이션을 이용한 금속복합재료 계면의 기계적 특성 연구

Abstract

The interfacial mechanical characteristics of metal matrix composites were investigated using a nanoindentation technique. Microstructure observations, tensile tests, and nanoindentation evaluations were carried out to determine the effect of interfacial microstructure on the mechanical properties of SiCp/Al composites.Silicon carbide particle (SiCp) reinforced aluminum (Al) matrix composites with different interfaces were fabricated using a conventional powder metallurgy method. Surface treatments such as electroless Ni coating and thermal oxidation were applied to SiCp for the formation of alternative interfacial microstructures. XRD analyses and TEM observations revealed that the SiCp/Al interface was significantly altered by the surface treatment of particles. In the case of uncoated SiCp, no interphase or diffusion layer was found, but Al4C3 formed partially on the SiCp. In the case of coated SiCp, alternative interfacial structures were found to be developed that suppressed the formation of Al4C3. Nanoindentation was performed to evaluate the interfacial mechanical characteristics of the composites. Nanoindentation is not only suitable for measuring hardness and elastic modulus on a micro-scale but can also provide the information regarding interfacial failure mechanisms. Nanoindentation profiles across the SiCp/Al interfaces showed the gradient of the mechanical properties around the particles and the variations in their matrix properties caused by interfacial reactions. Interfacial breakage test was used to evaluate the role of interfacial microstructures in the fracture of the composites. The failures of the interfacial regions were detected by interpreting the indentation curves. The aspect of the interfacial failures differed according to their interfacial microstructure, and their relative interfacial strengths were compared.The results of tensile tests agreed to a significant extent with the nanoindentation investigations. The fractured surfaces of the composites showed different interfacial characteristics, as inferred from the nanoindentation results.