Glass-Forming Ability and Crystallization Behavior in High-Density Bulk Metallic Glasses

Abstract

ABSTRACTAlloys of composition (Hfx,Zr1-x)57Ti5Cu20Ni8Al10 and (Hfx,Zr1-x)52.5Ti5Cu17.9Ni14.6Al10, where x = 0, 0.2, 0.4. 0.6, 0.8, and 1.0, were evaluated for glass-forming ability, and the devitrification behavior on heating of the (Hfx,Zr1-x)52.5Ti5Cu17.9Ni14.6Al10 glasses was examined. Glass-forming ability was determined by suction casting 3-mm-diameter rods, followed by neutron diffraction examination. Results show that substitution of Hf for Zr in these alloys degrades glass-forming ability, and that this effect is more pronounced in compositions of the (Hfx,Zr1-x)57Ti5Cu20Ni8Al10 type. To examine devitrification behavior, thermal analysis was used to identify temperatures at which exothermic events occurred on heating in the (Hfx,Zr1-x)52.5Ti5Cu17.9Ni14.6Al10 series. The amorphous alloys were then subjected to annealing treatments corresponding to the exothermic events. Crystal structures formed during annealing were probedby neutron diffraction, and the size scale of features developed examined by small-angle neutron scattering. Results show that the initial decomposition produces a structure witha characteristic length scale, but it is not yet possible to comment on the mechanism.