Wettability and Interfacial Reactions Between Metallic Glass Melts and Cu/Mo Used as Roller Materials for Twin-Roll Casting

Twin-roll casting has been recently revealed to be an efficient technique to produce rejuvenated metallic glass (MG) strips. Due to the high melting point and high hardness, pure Mo is considered as a good roller material as pure Cu. However, the wettability and interfacial reactions between MG melts and Cu or Mo remain largely unknown. In this work, a series of sessile droplet wetting experiments are designed to investigate the wettability and reactions between Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 (Vit.1) or (Zr_0.401Ti_0.133Cu_0.118Ni_0.101Be_0.247)₉₉Nb₁ (Nb1) MG melts and Cu/Mo substrates at temperatures of 1073, 1123 and 1173 K. It is found that the wettability and interfacial reactions of the Vit.1 and Nb1 MG melts on the Cu substrates are very similar. The equilibrium contact angles are ~ 30° at 1073 K and ~ 25°-27° at 1123 K. The MG melts completely spread out on the Cu substrates at 1173 K. Cu substrates are slightly dissolved in the MG melts event at 1073 K, and a transitional reaction layer exists between the droplet and the Cu substrate. In comparison, the Vit.1 MG melt exhibits a much improved wettability on the Mo substrate. The equilibrium contact angle of the Vit.1/Mo is only 6° at 1073 K and 5° at 1123 K. No significant diffusion of Mo into the droplet occurs even at 1173 K with a holding time of ~ 30 min. The interfaces of the Vit.1/Mo samples are sharp, and no interfacial reaction layers form. These findings indicate that pure Mo can be a good roller material for twin-roll casting at high temperatures, and the Mo-made rollers are expected of capability to produce MG strips with good quality.