Strategy for tailoring thermoplastic forming process incorporating the influence of process variables in bulk metallic glasses

Abstract

The technical interest in bulk metallic glasses (BMGs) has grown over the past few decades due to their potential for new areas of applications based on thermoplastic forming (TPF), which was previously unattainable in conventional crystalline alloys. However, the difficulty in controlling the TPF process due to the metastability of the amorphous phase has posed a barrier to widespread commercial use. This study provides practical guidelines for tailoring the TPF process incorporating the influence of process variables in BMGs. Specifically, we constructed a continuous heating transformation (CHT) diagram with iso-viscosity contours for LM1b (Zr44Ti11Cu10Ni10Be25) using Flash-DSC measurement. As an example of a TPF process utilizing the obtained CHT diagram, we demonstrated three TPF procedures from bulk to nano scales, namely BMG pressing, BMG joining, and hologram nanopatterning. Interestingly, with increasing heating rate, the TPFA is enhanced, although the incubation time for crystallization decreases. Furthermore, we proposed a new TPFA parameter, P, which considers both the supercooled liquid viscosity and crystallization kinetics to compare the TPFA of various BMGs. Especially, we constructed a plot depicting the correlation between P and calculated maximum elongation, and heating rate to investigate quantitatively the relationship between TPFA and heating rate. These results will enable us to select the most suitable BMG for the targeted applications and precisely optimize the TPF processes, which could lead to further improvements in their performance and expanded applications in various industries.