Sheet fabrication of bulk amorphous alloys by twin-roll strip casting

Modelling and simulation of twin-roll casting of bulk metallic glasses

“…As found in the literature [1,3] the microstructure of the cast strip will contain a small amount of crystalline particles which are present prior to casting. A melting procedure including a period designed to completely melt all particles followed by stabilising at a temperature low enough to ensure crystallization will not occur may be employed to eliminate any crystalline particles present prior to casting.…”

“…TRC, which can achieve high cooling rates (10 2 -10 3 K/s) has been examined as a possible method to continuously produce BMG strips [1][2][3]. Various problems were encountered such as: achieving the cooling rates required, selecting an optimum casting speed taking into account the low conductivity of metallic glass and determining the HTC between rolls and the strip.…”

“…Three assumed values, increasing for three distinct stages of the process, where chosen based on the range of HTC specified by literature [1,3] 0.15 (Wcm -2 K) 0.25 (Wcm -2 K) 0.40 (Wcm -2 K) The diameter of the rolls chosen for the model was 20 cm and the strip thickness was initially chosen as 2mm.…”

“…The material properties and process parameter for Vit 1 which were required to run the model were obtained from the literature [1,3] Over the same range of casting speeds as used in the binary alloy model (1-5cm/s), it was found that the Vit 1 strip exits at sufficient low temperatures to remain strong enough to ensure continuous casting. The matter of interest is then whether the strip is fully amorphous throughout or if it contains some crystalline particles.…”

“…The matter of interest is then whether the strip is fully amorphous throughout or if it contains some crystalline particles. The research carried out by Lee et al [1,3] set two criteria for the successful casting of a fully amorphous strip.…”