Tensile fracture dynamics and intrinsic plasticity of metallic glasses

Under tensile tests of metallic glasses (MGs) subjected to annealing below glass transition temperature T-g, ductile-to-brittle transition (DBT) occurs due to structural relaxation, which results in more ordered atomic packing and decrease of glass fraction phi. DBT is observed simultaneously with fracture mechanism transition: shear banding to cracking. All MG samples annealed under different temperature were also restricted to shear banding and cracking separately under small-aspect-ratio compression and compact tension avoiding DBT. Experimental results prove that as annealing temperature increases (or glass fraction phi decreases), strength for shear banding increases, while strength for cracking decreases; as phi becomes less than critical state phi(DBT), MG samples tend to cracking instead of shear banding. So, phi(DBT) is proposed as an important parameter to characterize the intrinsic plasticity of various MGs and to conform to the previous factors soundly. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789439]