An Al_2O_(3f)/Al-4.5Cu composite was made by squeeze casting. The solutesegregation in the composite at different cooling rates was studied. The results indicate that theprimary crystal of Al-4.5Cu alloy nucleates and...An Al_2O_(3f)/Al-4.5Cu composite was made by squeeze casting. The solutesegregation in the composite at different cooling rates was studied. The results indicate that theprimary crystal of Al-4.5Cu alloy nucleates and grows in the interstice between fibers. The fibersurface cannot serve as site for the heterogeneous nucleation of a primary dendrite. There exists anincreasing Cu concentration gradient from the center of the interstice between fibers to theinterface or the grain boundaries. There are the eutectic phases around the fibers. The solutesegregation in the matrix increases with the cooling rate rising. The amount of eutectic phasesfollowed by imbalance crystalline can be numerically calculated with Clyne-Kurz formula.展开更多
Formation of icosahedral dusters in rapidly solidified binary amorphous NixZr100-x （x = 15, 33.3, 50, 66.7, 85） is studied by using molecular dynamics simulation methods. A large number of icosahedral dusters with 1...Formation of icosahedral dusters in rapidly solidified binary amorphous NixZr100-x （x = 15, 33.3, 50, 66.7, 85） is studied by using molecular dynamics simulation methods. A large number of icosahedral dusters with 13 atoms （Ih13） were observed in NixZr100-x alloys, and most of them, even those in Zr-rich alloys, are found to be Ni-centred. Studies on the structures of Ni33.3Z66.7 obtained at different cooling rates demonstrate that most of iscosahedral dusters enhanced by decreasing cooling rates are also Ni-centred, The essentials of Ni atoms preferring to be the core of icosahedral clusters are illustrated with the criterion of energy minimization and the equilibrium interatomic distances between different atoms.展开更多
文摘An Al_2O_(3f)/Al-4.5Cu composite was made by squeeze casting. The solutesegregation in the composite at different cooling rates was studied. The results indicate that theprimary crystal of Al-4.5Cu alloy nucleates and grows in the interstice between fibers. The fibersurface cannot serve as site for the heterogeneous nucleation of a primary dendrite. There exists anincreasing Cu concentration gradient from the center of the interstice between fibers to theinterface or the grain boundaries. There are the eutectic phases around the fibers. The solutesegregation in the matrix increases with the cooling rate rising. The amount of eutectic phasesfollowed by imbalance crystalline can be numerically calculated with Clyne-Kurz formula.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50225103 and 50471001.
文摘Formation of icosahedral dusters in rapidly solidified binary amorphous NixZr100-x （x = 15, 33.3, 50, 66.7, 85） is studied by using molecular dynamics simulation methods. A large number of icosahedral dusters with 13 atoms （Ih13） were observed in NixZr100-x alloys, and most of them, even those in Zr-rich alloys, are found to be Ni-centred. Studies on the structures of Ni33.3Z66.7 obtained at different cooling rates demonstrate that most of iscosahedral dusters enhanced by decreasing cooling rates are also Ni-centred, The essentials of Ni atoms preferring to be the core of icosahedral clusters are illustrated with the criterion of energy minimization and the equilibrium interatomic distances between different atoms.
