chapter  21

Metallic Nanoglasses Investigated by Molecular Dynamics Simulations

WithD. Şopu, O. Adjaoud

The history of metallic glasses starts in 1960, at California Institute of Technology, when Duwez et al. [1] discovered the first binary metallic amorphous alloy Au80Si20. They developed rapid quenching techniques for cooling metallic liquids at very high rates of about 106 K/s. At this cooling rate, atoms do not have enough time or energy to rearrange for crystal nucleation and the material is frozen in an amorphous state. The atoms retain an amorphous distribution, i.e., random packing with no long-range order. The very high cooling rate required to produce metallic glasses restricts the specimen geometry to thin ribbons, foils and powders with sizes of the order of microns [2] and hinder their application range [3]. In order to slow down the crystallization kinetics when quenching a melt and form metallic glasses with high glass-forming ability, multiple components alloys are required. Following, in the early 1980s, glassy ingots were casted with thickness of 1 cm and obtained the first bulk metallic glass (BMG) [4]. Perhaps the most popular commercial BMG is a pentary alloy based on Zr-Ti-Cu-Ni-Be with a critical casting thickness of up to 10 cm [5] and became known as Vitreloy 1, developed by Johnson and Peker in a project funded by NASA to develop new aerospace materials. Besides the technique of rapid quenching from the liquid state, other production routes such as vapor deposition (inert-gas condensation) [6], solidstate amorphization reactions, e.g., ball milling [7], or amorphization by high energy radiation [8] have been extensively developed and elaborated for the purpose of producing a wide variety of metallic glasses.