Nanoengineering metallic glasses

Metallic Glasses represent an interesting class of materials, as they can combine high strength and attractive functional properties. Unfortunately, like window glass, they break catastrophically. In standard metals the movement of trillions of defects (imperfections in the regular atomic arrangement) can lead to permanent deformation. An aluminum foil can be easily deformed without breaking. In contrast, in metallic glasses the atoms are more randomly arranged. There are no movable defects. Therefore, when trying to deform the sample, large forces build up locally and the material breaks starting from a very localized region. This process is similar to the start of an earthquake. To prevent the material from breaking, it is important to alter the atomic structure such that the deformation is better distributed. Recent research efforts are focusing on controlling local heterogeneities in the structure by making additional space between the atoms, by changing the local composition of elements and by adding elements such as oxygen. However, systematic studies on contribution of these individual factors are lacking. The reason is that typically in metallic glasses the way atoms are arranged (the structure) and the type of atoms (the composition) are closely connected. Especially the effect of oxygen addition is still not fully understood. Therefore, in the present project it is planned to use sputter deposition, where the material is built up from individual elements. Both, structure and composition can be controlled. In addition, larger samples will be made by rapidly cooling the liquid metal. The structure and mechanical properties of the samples will be studied using a wide range of modern experimental techniques, ranging from the mm to the individual atom. Additionally, in the computer large models mimicking the experiment will be analyzed. This combination should help to formulate strategies to prevent fracture in metallic glasses. To reach this challenging goal, the project combines the expertise from two groups, the Erich Schmid Institute of Materials Science, Austrian Academy of Sciences and the Laboratoire des Sciences des Procédés et des Matériaux, French National Centre for Scientific Research.