Enhanced tensile strength and ductility of bulk metallic glasses Zr_(52.5)Cu_(17.9)Al_(10)Ni_(14.6)Ti_5 via high-pressure torsion

摘要

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 run inside the amorphous matrix are observed after 30 turns HPT. Free volume increases from ～0.9030 A~3 (as cast) to ～0.9275A~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 ductiliza-tion 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.