Viscous Flow Deformation in Supercooled Liquid State of Bulk Amorphous Zr55Al10Ni5Cu30 Alloy

Abstract

The deformation behavior in the supercooled liquid region for the amorphous Zr₅₅Al₁₀Ni₅Cu₃₀ alloy was examined as a function of temperature, applied stress and deformation rate. The deformation occurs through the Newtonian viscous flow with the strain rate sensitivity (m value) of approximately 1.0. By utilizing the ideal superplastic flow, the extrusion with an extrusion ratio of 3.6 for the cast amorphous Zr–Al–Ni–Cu cylinder was easily made in the condition where the extrusion temperature was in the range of 703 to 743 K and the extrusion velocity was 0.67 to 22 μm/s. The extruded alloy also keeps an amorphous phase and no appreciable difference in the mechanical properties is seen between the cast and extruded amorphous alloys. However, a distinct endothermic reaction is observed around the extrusion temperature on the differential scanning calorimetric curve of the extruded alloy. The endothermic reaction is due to the structural change from the relaxed disordered atomic configurations developed by extrusion to internally equilibrium disordered atomic configurations. The evidence on the modification in the disordered structure during the severe deformation of the supercooled liquid is important for future development of basic science and engineering utilization of the supercooled liquid.