Changes in the crystallization sequence upon sulfur addition in the Zr$_{52.5}$Cu$_{17.9}$Ni$_{14.6}$Al$_{10}$Ti$_{5}$ bulk metallic glass-forming liquid revealed by in situ high-energy x-ray diffraction

Bulk metallic glasses (BMGs) surpass the strength of steels and possess the elasticity and formability of polymers. The key to obtain these properties is to conserve the amorphous structure of a metallic melt and avoid crystallization during processing. In this work, a change in the crystallization sequence in the widely used BMG Zr$_{52.5}$Cu$_{17.9}$Ni$_{14.6}$Al$_{10}$Ti$_{5}$ (Vit105) upon the addition of sulfur (Zr$_{51.45}$Cu$_{17.54}$Ni$_{14.31}$Al$_{9.8}$Ti$_{4.9}$S$_2$; Vit105 S$_2$) is revealed by in situ high-energy x-ray diffraction, both upon heating from the glassy state and upon cooling from the liquid state during electrostatic levitation. This methodology proves to be a powerful tool to elucidate the complete crystallization behavior of complex BMG-forming liquids. The experiments show that the addition of sulfur changes the crystallization sequence and phases in a different manner upon cooling from the liquid state than upon heating from the glassy state. The thermal stability at low temperatures upon heating is increased, as the supercooled liquid region is extended from 60 to 77 K and the glass transition temperature increases from 671 to 692 K. However, the thermal stability is decreased upon cooling, causing a reduced glass-forming ability