Assessing continuous casting of precious bulk metallic glasses

This study describes investigations of continuous casting for the bulk metallic glass-forming alloys Pd43Ni10Cu27P20 and Pt57.3Cu14.6Ni5.3P22.8, respectively. Continuous casting of the Pd-based alloy readily produced fully amorphous rods of 10 mm diameter and >500 mm length. In contrast, the Pt-based alloy always underwent crystallization during the casting process, even at smaller rod diameters down to 2 mm. In search of the reason for this difference, we simulated the process using ProCAST. Via adapting the heat transfer coefficients for all the relevant interfaces of the continuous casting setup we obtained good agreement between the experimental temperature data and the simulations. The calculations revealed that the maximum cooling rates achievable with this industrial setup ranged from 15 K/s to 17 K/s. This is well above the critical cooling rate for glass formation of the Pd-based alloy, but below that of the Pt-based alloy, as inferred from literature data and corroborated by fast differential scanning calorimetry. These findings illustrate how detailed casting simulations can predict the feasibility of semi-industrial bulk metallic glass production techniques.