Synthesis of Al-rich bulk metallic glass composites by warm extrusion of gas atomized powders

Highlights: ► Bulk Al-rich metallic glass composites were fabricated by warm extrusion of gas-atomized amorphous powders. ► The viscosity dependence of the powders upon temperature was analyzed by calculation and confirmed during warm extrusion. ► The consolidated compacts are composed of the structure of Al nanophase embedded in amorphous matrix. ► The formation of devitrified structures is mainly related to the deformation-induced temperature rise during extrusion. -- Abstract: Centimeter-scale Al85Ni5Y6Co2Fe2 bulk metallic glass composites were fabricated by warm extrusion of gas-atomized amorphous powders. Thermal behavior and microstructure of both the starting powders and the extruded samples formed with different extrusion ratios were studied in detail. The viscosity dependence of the powders on temperature was analyzed by calculation. The result demonstrated that the viscosity decreases steeply near the glass transition temperature and the minimum viscosity value calculated is about 1.37 × 108 Pa s at 550 K. Those have been confirmed by the viscous flow in warm extrusion around such a temperature. The compacts consolidated at 550 K under various extrusion ratios from 6.8 to 15.7 yielded nanostructured α-Al/glassy matrix composites with high hardness. The appearance of such a devitrified structure is thought to be related to the deformation-induced temperature rise during extrusion