WEB Plasticity of topologically close-packed phases in the Co-Nb systemWednesday (01.01.2020) 01:15 - 01:30 Part of:
Advanced structural materials with high strength and temperature capabilities are crucial in sustainable energy conversion and transport technology of the future. The topologically close-packed (TCP) phases such as the Laves phase and µ phase are promising candidates for high-temperature applications. Alloys reinforced with high melting point TCP phases are economically and ecologically efficient materials that can replace high-temperature steels in power plants or superalloys in various turbine applications. There are a tremendous amount of TCP phases but our knowledge of their mechanical properties and deformation mechanisms is quite incomplete. The complex TCP phases with large unit cells are composed of a few fundamental building blocks. The idea of considering the deformation of complex TCP phases based on their essential building blocks, which govern their plasticity, would greatly simplify the analysis and allow a transfer of knowledge to the other complex intermetallic phases. In the Co-Nb system, there are different types of TCP phases including three NbCo2 Laves phases and the Nb6Co7 μ-phase. In the present work, the mechanical properties and deformation mechanisms of the Nb6Co7 μ-phase were studied and compared with those of the NbCo2 Laves phases. Hardness and indentation modulus were measured by nanoindentation. Micropillar compression tests were performed to study the deformation mechanism at room temperature and the critical resolved shear stress of the Nb6Co7 μ-phase. Electron backscatter diffraction (EBSD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) were used to identify the deformation mechanisms. The influences of the structure and composition on the mechanical properties of the TCP phases are discussed.