Electroplastic forming in a Fe-based metallic glass ribbon

Abstract

Electric current has been applied to lower the temperature and loading required for metalworking of extremely strong or brittle alloys. However, limited studies have been conducted on the electrically-assisted forming of metallic glasses. Our previous study revealed the feasibility of electroplastically deforming a Fe 78 B 13 Si 9 metallic glass ribbon. Yet the drawback is that pre-stressing was required prior to electropulsing and large elastic recovery limited the dimensional accuracy of the forming process. In the present work we demonstrate a setup in which metallic glass ribbons were subjected to punching, with electropulsing applied simultaneously in various combinations of frequency and punching speed. Process temperature was measured to be significantly below the glass transition temperature and the process only takes 20-30 s. Lower load was required to punch the ribbon with electrical pulses applied. All the ribbons were fully deformed without spring back after the punch was retracted. X-ray diffraction revealed that all ribbon were essentially amorphous, with only some rare cases suffering from embrittlement. It is concluded that electric current provided a directional force acting as an aid to overcome the activation barrier of shear transformation zones; however, as a side effect joule heating also accelerated beta relaxation causing the embrittlement. This study revealed a novel way of shaping metallic glasses with the potential of industrial scale application. ? 2015 Elsevier B.V.. All rights reserved.