Basic Research on Precision and Micro Machining of Metallic Glasses. Deformation Behavior of Zr Based Bulk Metallic Glass under Tensile Stress.

Abstract

Deformation behavior of Zr based bulk metallic glass ; Zr55Cu30Al10Ni5 (atomic %) under tensile stress at the supercooled liquid region was observed. The bulk metallic glass was produced by die casting into a copper mold at vacuum atmosphere. The amorphicity of cast bulk alloy and the crystallization behavior of the amorphous phase were tested by X-ray diffraction (XRD) and differential scanning calorimeter (DSC) respectively. Machined specimen was tensed at 713 K, 723 K and 733 K (in the supercooled liquid region) at various strain rates between 4.25 × 10-3 s-1 and 2.90 × 10-1 s-1. The supercooled liquid exhibited a Newtonian viscosity and superplastic-like behavior during tensile deformation. The bulk metallic glass was elongated as much as 1 000% at high strain rates ranging from 2.50 × 10-2 s-1 to 2.00 × 10-1 s-1. The largest elongation reached 1 700%, and the smallest breaking diameter was 27 μm. However, crystallization in tested specimen was observed. The crystallization of this bulk metallic glass has a tendency to be promoted under tensile deformation.