Influence of viscous flow on the deformation behavior of bulk metallic glassy alloys in supercooled liquid region

We present the investigation of the effect of viscosity on the deformation behavior of metallic glasses at supercooled liquid region during hot extrusion. Also the change of the specific surface area in porous Hf-based metallic glass and Ni-based metallic glass were compared. The homogeneously distributed ruggedness-shape surface of ligament was observed in the Hf-based metallic glass which has lower viscosity comparing to that of Ni-based metallic glass. For lower viscosity, it is very desirable to fabricate large surface area porous metallic glass due to a change of the surface morphology of the ligaments from smooth-like to rugged-like appearance, thus suggesting an optimum regime for increasing the specific surface area by controlling viscosity of metallic glass at a given processing condition.