A Forming Load Prediction Model in BMG Micro Backward Extrusion Process Considering Size Effect

The size effect was considered in order to improve the prediction accuracy of forming load in the micro backward extrusion process of a Zr55Cu30Al10Ni5 BMG cup-shaped specimen. The ratio of the billet surface to volume near the working land of backward extrusion punch was proposed as size effect factor. Then the size effect factor was complemented into a backward extrusion load prediction formula of conventional macroscopic parts. The micro-sized BMG cups with different sidewall thickness varying from 20 μm to 125 μm were deformed in supercooled liquid state. The initial diameter of the billets is 600 μm and the experiments were conducted at Zwick/Roell Z200 Press. The forming loads were recorded and compared with the calculated values from the proposed prediction model. The results showed that the proposed model can predict the forming load with very small deviation.