Fabrication of Ta-Reinforced Cu-Based Bulk Metallic Glass Composites by High-Pressure Torsion

Ex situ Cu54Zr22Ti18Ni6 matrix bulk metallic glass composites (BMGCs) reinforced with Ta particles (10-30 vol.%) were fabricated by high-pressure torsion (HPT) under applied pressure of 6 GPa for 1-3 turns at temperatures of 25 or 200 degrees C. The densification, structure, thermal, and mechanical properties of BMGC samples were investigated by Archimedes densitometry, optical microscopy, x-ray diffraction, differential scanning calorimetry, small punch test, and microhardness measurements. Near full-density BMGC disks (relative densities higher than 0.97) are fabricated using HPT, irrespective of the processing strain and temperature. The microhardness of BMGCs is improved by increasing the number of turns, or the processing temperature due to the improvement in the deformation degree of both the amorphous and Ta particles as well as the reduction in the interlayer spacing of Ta particles. Nevertheless, there is an optimal amount of Ta which gives rise to the peak hardness in the BMGC samples, depending on the amount of imposed strain during HPT. The results of small punch test indicate that the addition of Ta to the monolithic BMG and increasing the HPT temperature significantly enhance the fracture load and deflection.