Growth kinetics of Cu-Zr

Abstract

The Cu-Zr alloy system has attracted great interest due to its high glass-forming ability. Using electrostatic levitation technique we are able to undercool the melt of Cu-Zr by more than 300 K and investigate the solidification process when approaching the glass transition temperature. High- speed video recording of the crystallization event enables us to determine the velocity of the solidification front at different undercoolings. For the Cu-Zr system, we observe an unusual behavior. While for usual binary alloys, the growth velocity increases with increasing undercooling, we find for the Cu-Zr system that the growth velocity reaches a maximum around 200 K and decreases when the amount of undercooling is further increased. To determine the primary phase that occurs during solidification, we have performed in-situ x-ray diffraction measurements at the beamline BW5 at HASYLAB. We find that the unusual behavior of the growth velocity cannot be explained by phase selection during rapid solidification of the deeply uncercooled melt. Experiments in microgravity are planned onboard the international space station (ISS) to investigate the influence of convection that might play a role with regard to the small growth velocities observed for the Cu-Zr alloy system. We thank the DFG for financial support by grant HE1601/26.