Enhancement of room-temperature plasticity in a bulk metallic glass by finely dispersed porosity

Abstract

Melts of ${\mathrm{Pd}}_{42.5}{\mathrm{Cu}}_{30}{\mathrm{Ni}}_{7.5}{\mathrm{P}}_{20}$ (at. %) held under pressurized hydrogen are cast into bulk metallic glass (BMG) rods with fine ($20–30\mu \mathrm{m}$ diameter) pores uniformly dispersed. The low overall porosities $(<4\%)$ lead to only small reductions in Young modulus and yield strength, but to dramatically enhanced plasticity in compression: Rupture energy as high as $295\mathrm{MJ}{\mathrm{m}}^{-3}$ , compared to $16\mathrm{MJ}{\mathrm{m}}^{-3}$ for the pore-free BMG. The pores force the proliferation of shear bands below the overall failure stress, a process of interest for toughening BMGs, materials for which shear localization in deformation restricts structural applications.