Thermomechanical Adhesion between Metallic Glass and Die Materials

Thermoplastic forming is a promising method for fabricating metallic glass (MG) products with complex shapes. This method can avoid the difficulties encountered in other manufacturing processes, such as very high cooling rate required by casting and catastrophic cracking in machining. However, during thermoplastic forming the adhesion between dies and MGs restricts the production. It is therefore important to explore the underlying adhesion mechanisms during forming and establish guidelines for selecting proper die materials. In this paper, we comprehensively studied the adhesion between La-based MG and some widely-used die materials (electroless Ni-P, Si, alumina and silicon nitride) in the thermoplastic forming process. It was found that, among these die materials, alumina has the best performance, which is attributed to its strong chemical bonds and low surface energy. The study concludes that the surface energy and the type of chemical bonds can be proper indicators for selecting die materials.