Investigation of Formation, Stability, and Structure of Quasicrystal and Related Crystalline Phases

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This is grant is directed to experimental research on icosahedral phase formation and stability in selected alloys. Emphasized are (1) determination of the atomic structure of the bcc Ti-Cr-Si approximant from precision powder and single crystal X-ray diffraction studies; (2) expansion of the investigation into related phases discovered in the Ti-Zr transition metal alloys; (3) measurement of low and high temperature resistivity in bcc Ti-Cr-Si to compare with the transport properties already measured in Al crystalline approximants; (4) estimation of the glass-to- icosahedral phase and glass-to-alpha phase interfacial energies in Al-Mn-Si; (5) extension of an atomic model for Al-Mn to predict the structure of Al-Co-Cu. %%% Research on icosahedral phase structure and stability provides an important link to metallic glasses and complex intermetallic alloys. Understanding formation of these phases is required for improved metal alloy design.