The Effect of Forming Speed on the Formability of a Zr-Based Bulk Metallic Glass

Abstract

Taking cup-shaped part (outer diameter D and wall thickness are chosen as 2.2 mm and 0.05 mm, respectively) as an example, the micro-back-extrusion forming process of a Zr55Cu30 Al10Ni5 bulk metallic glass (BMG) in its supercooled liquid region was studied by using finite-element analysis (FEM) and experiment. The effect of forming speed on the formability was analyzed based on the extrusion load, the rheological behavior of the material and the microstructure of the formed parts. It was found that while the forming speed is below than 4 μm/s, the extrusion load increases obviously with the increasing in forming speed, otherwise, the BMG will follow non-newtonian flow and the forming load is insensitive to the forming speed. The parts fabricated at 2 μm/s are obviously crystallized due to the long retention time of metallic glasses at high temperature, a higher forming speed is benefit to enhancing the formability if the BMG. On this basis, micro cup-shaped parts with only 0.05 mm in wall thickness are successfully extruded.