Fabrication of Mg-based bulk metallic glass molds by thermal imprint process

Bulk metallic glasses (BMGs) have exhibited high strength, low surface energy and superior glass-forming ability. At temperatures above the glass transition temperature, BMGs become supercooled viscous materials and can be formed into complicated shapes or patterns on micro- or nano-scales. Therefore, BMGs have been considered to replicate molds for micro/nano forming applications. In this study, Mg58Cu31Y6Nd5 bulk metallic glasses were applied to study the fabrication of BMG molds from nickel master molds with micro structures by thermal imprint process. Theoretical and experimental studies were performed to understand the filling process of mold replication. A commercial computational fluid dynamics software based on the finite volume method (FVM) was used for simulating the filling behavior, where the FVM predictions reasonably well agreed with experimental measurements. With adequate operation parameters, both simulation and experimental results showed that filling rate was up to 97%. The replicated BMG molds were then employed to fabricate micro structures on PMMA substrates. It was found that the fabricated micro structures were easy to be released from the BMG molds and they gave almost the same geometrical features as that on the original master molds. Mg-based bulk metallic glasses showed good formability for replicating molds with fine structures in this study and they could be applied to micro/nano imprint applications in the future.