We report experimental evidence of in-situ Mg77Cu12Zn5Y6 bulk metallic glass (BMG) ma- trix composite with extraordinary plastic strain of 18.5% and specific strength of 4.31×105 N·m·kg?1, which are the highest plasticity and specific strength in Mg base BMG alloys reported to date. The excel- lent mechanical properties are attributed to the for- mation of the composite structure which is composed of amorphous matrix and hexagonal-close-packed (hcp) Mg solid solution needle phase with a width less than 500 nm. As plastic phase, the Mg needles not only possess the capability of deformation but also have work hardening phenomenon effect. They give rise to multiple shear bands, and hinder the propagation of local shear band in amorphous matrix.
HUI Xidong DONG Wei WANG Meiling LIU Xiongjun YU Jialing CHEN Guoliang
The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission electron microscopy (HRTEM) techniques. We focused on the short-range order (SRO) and medium-range order (MRO) in the glassy structure. It is shown that there are icosahedral,FCC-and BCC-type SROs in the Zr-based metallic glasses. A structural model,characterized by imperfect ordered packing (IOP),was proposed based on the MD simulation and confirmed by the HRTEM observation. Furthermore,the evolution from IOP to nanocrystal during the crystallization of metallic glasses was also ex-plored. It is found that the growth from IOP to nanocrystal proceeds through three distinct stages: the formation of quasi-ordered structure with one-dimensional (1D) periodicity,then 2D periodicity,and finally the formation of 3D nanocrystals. It is also noted that these three growth steps are crosslinked.
Single crystalline Bi2O3 nanosheets have been synthesized by the surfactant assisted solvothermal method,using oleic acid and sodium dodecyl benzene sulfonate (SDBS) as compound surfactants. The thickness of Bi2O3 nanosheets is 40–70 nm with a monoclinic crystal structure. High-resolution transmission electron microscopy observation reveals that ( 345 ) lattice plane of the single crystal is parallel to the surface of the nanosheets. The cooperative effect of oleic acid encapsulated SDBS is the key to form single crystalline α-Bi2O3 nanosheets with a preferred growth orientation. An obvious blue shift of the single crystalline Bi2O3 nanosheets with a preferred surface ( 345 ) is observed due to quantum confinement effects in thickness and optical anisotropy.
