Chuang Dong

Abstract:

Metallic alloys follow well-established composition rules but their complex chemistries are not yet understood so far, despite their long history and close ties with our daily life. The present talk addresses this fundamental question using a new structural approach, the cluster-plus-glue-atom model, which gives simple composition formulas for all kinds of metallic alloys including quasicrystals, metallic glasses, and solid-solution-based industrial alloys. This model dissociates any structure into a 1st-neighbor cluster plus a few outer-shell glue atoms, so that it can be expressed in terms of the cluster formulas as [cluster](glue atoms). I will first present the pathway that leads to the proposition of this new theory, which dates back to the good old days working with Prof. Jean-Marie Dubois at the Ecole des Mines de Nancy in the late 80¡¯s and early 90¡¯s. Then I will discuss the basics about the model and the physics behind. Finally, I will use the model to analyze alloy examples covering Al-based quasicrystals, bulk metallic glasses, and solid solution alloys. I will point out their common structural origins within the framework of our model. The revelation of the composition formulas points to the common existence of simple composition rules behind seemingly complex chemistries of different kinds of alloys, thus offering a practical and fundamental method towards their composition interpretations and eventually designing.