Experiment And Finite Element Analysis On Micro Forward Extrusion Process With Amorphous Alloy

The micro forward extruding behavior of Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass in its supercooled liquid region was studied using self-made extrusion dies and Zwick/Roell electronic materials testing machine. The micro extrusion process was also simulated based on Deform-3D finite element software.The copper mold casting method was used to produce Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass. The structure and thermal properties of the sample were analyzed by using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) methods. Its supercooled liquid region was determined to be 411℃⁴97℃.The traditional extrusion die system does not apply to the micro forming process. In order to overcome this defect, a new micro forward extrusion die system was designed and manufactured with several novel concepts such as the self-guided and half-die structure. The die material is H13 hot die steel.Based on the similarity theory, the micro forward extrusion experiment with different specimen sizes (Φ2×H3,Φ1×H1.5,Φ0.5×H0.75mm) using extruded dies of different length (1, 6.5mm) were conducted at temperature 450℃, 460℃and strain rates 0.001⁰.01s-1. The results indicate that, the unit pressure of upper die increases with the decrease of specimen size and the tendency of forming load even changes when the specimen size decreases toΦ0.5mm. Also, when the specimen is extruded in the short die under 450℃, the unit pressure is lager than that of which is extruded in the long die under the same temperature. However, when 460℃is chosen, the conclusion above is opposite. At last, the swell ratio of the extruded specimen which increases with the decrease of specimen size or the increase of strain rate is about 10%³6%.The micro forward extrusion process of bulk metallic glass in the supercooled region was simulated using Deform-3D finite element software. The results indicate that, the extrusion behavior of metallic glass can be better simulated at lower strain rate than at higher strain rate using current material model. Also, the simulation can accurately reflect back the phenomenon that the unit pressure of upper die increases as soon as the specimen be extruded out of the die exit.