Cooling conditions for the generation of bulk metallic glass by droplet deposition

Abstract

Bulk metallic glasses are in the focus of international research activities for about 30 years. But in the past, little attention has been given to advanced production techniques such as deposition molten metal sprays or spray forming to generate bulk metallic glasses. In this work the cooling conditions of droplets during spray forming were investigated due to its utmost importance for producing amorphous structures. Spray forming is a three step cooling process consisting of droplet flight phase, splat phase and deposit phase. All cooling steps were simulated for different droplet sizes. The surface temperature of the deposit was found to play an important role for the production of metallic glasses by spray forming. Therefore, the influence of the melt flow rate on the deposit surface temperature was investigated. The model can be used to generate the specification of suitable spray conditions for the generation of bulk metallic glasses even for the compositions which are difficult to cast because of their low critical casting thickness.