| Metallic glasses exhibit a combination of favorable properties possessed by metals and glasses which is not easily duplicated by crystalline materials. Presently, most of the metallic glasses are produced by rapid melt quenching or vapor condensation. These processes employ rapid cooling to suppress nucleation and growth of the crystalline phases. The intrinsic disadvantage of rapid cooling is that about 60% of heat of fusion must be extracted in a very short time period which means that at least one dimension must be kept very small. The feasible geometrical shapes are thus limited to powders, ribbons, wires, and thin films etc.; Due to limited applicability of such shapes, it is requisite to develop means of producing the glasses into forms of greater utility. Since metallic glasses are easy to crystallize upon exposure to elevated temperatures, techniques such as sintering, hot isostatic pressing, and hot extrusion are inappropriate to consolidate metallic glasses into bulk form. The possibility to produce metallic glasses by using rapid pressurizing instead of rapid cooling is being investigated.; Using realistic potential functions obtained via the Embedded-Atom-Method, molecular dynamics simulation were performed to produce glassy states of Ag{dollar}sb{lcub}55{rcub}{dollar}Cu{dollar}sb{lcub}45{rcub}{dollar} by different preparation procedures. The present computer simulation work will furnish the basis for potential experimental work in the future. The pressurizing and quenching processes have been simulated and compared. The glass transition temperature and pressure have been obtained and their dependence on the initial state of the liquid alloy, the method of preparation and the rates of quenching and pressurization were investigated. The pair distribution function obtained for rapid cooling is consistent with the experimental data and the one for rapid pressurizing or quenching at an elevated pressure is in general consistent with the peak positions but with a slight different peak shapes.; In addition to the studies of metallic glass formation and properties, other phase transformations in metallic systems have been explored in order to provide information about the microscopic mechanisms of such phenomena. Moreover these studies provide further information and substantiate the use of the Embedded Atom Method for investigation of metallic systems. In these studies we have: (i) elucidated the structure and energetics of the crystal-to-liquid and liquid-to-vapor interfaces of Ni(100) and Ni(111) at equilibrium coexistence and (ii) investigated disordering and premelting phenomena at the (110) surface of Ni. |
