Rheological Behavior, Optimized Processing Interval, and Microreplication of a Zr‐Based Bulk Metallic Glass. Issue 7 (14th April 2018) - Song, Xinxiang
Abstract : Bulk metallic glass (BMG) is a novel advanced material developed since 1980s. In this paper, the Zr35 Ti30 Be27.5 Cu7.5 BMG is prepared and its thermoplastic forming (TPF) tests at various strain rate with different temperatures in supercooled liquid region (SCLR) are conducted. According to differential scanning calorimetry (DSC) curve and the transformed Kissinger equation, the normally processable temperature window (588–731 K) and continuous heating transformation (CHT) curve are obtained, respectively. And the isothermal annealing experiments without deformation are performed at 663, 683, 703, and 713 K with various holding times, respectively, results of which obviously suggest that the deformation during TPF can induce crystallization. Notably, from CHT curve and TPF tests, the optimized processing interval is subsequently revealed. All evidence indicates that this alloy presents good superplastic‐like behavior with a relatively low level of flow stress and large plastic strain under the temperature ranging from 643 to 703 K and the strain rate of 1 × 10 −2 s −1 –5 × 10 −4 s −1 . Furthermore, the successful microreplication and molding of several coins and microparts under the condition of strain rate of an order of 10 −3 s −1 at 663 K also provides us with the full proof for extremely good thermoplastic formability in this alloy. Abstract : In this paper, by making comparison of results among hot deformation, isothermal annealing and continuous heating transformation curve, the rough optimized processing interval has been given in Zr35 Ti30 Be27.5 Cu7.5 bulk metallic glass to avoid possible crystallization. In order to confirm its practical application and workability, simple microreplication and molding are performed, obtaining the complete replication surface and configurations of microparts.