Enhanced tensile strength and ductility of bulk metallic glasses Zr52.5Cu17.9Al10Ni14.6Ti5 via high-pressure torsion

Abstract

Zr 52.5 Cu 17.9 Al 10 Ni 14.6 Ti 5 (Vit105) Bulk metallic glass is processed by High-Pressure Torsion up to 30 rotations at room temperature, showing simultaneous enhancement of both strength (2023 MPa) and ductility (0.45%). Nano-crystal precipitates with an average size of 45 nm inside the amorphous matrix are observed after 30 turns HPT. Free volume increases from ~0.9030 Å 3 (as cast) to ~0.9275Å 3 after 30 turn HPT alloy with 2.83% (by volume) of nanocrystal precipitates. Strengthening due to precipitation after 30 turns HPT comply with the phase mixture model. The synergetic effect of free volume and nanocrystal precipitation on the ductility of amorphous-crystallite composite is quantitatively approached through modelling. By implementing the model, a ductilization window between bottom limit and top limit of the inter-crystallite spacing w.r.t the free volume is established, elucidating the necessary conditions required to obtain plasticity in amorphous-crystalline composites. • Both ductility and strength of BMGs are enhanced by HPT processing. • The nanocrystals precipitation during HPT increases the strength. • Free volume increase during HPT enhances ductility and reduces yield stress. • Synergetic effect of free volume and nanocrystals on ductility was observed. • Mechanism based-modelling correctly predict the synergetic effect on ductility.