Enhanced plasticity in laser additive manufactured Nb-reinforced bulk metallic glass composite

The microstructures and mechanical properties of 50 wt% Nb-reinforced Zr-based bulk metallic glass composites, (BMGCs), manufactured via laser directed energy deposition (LDED) with two different laser powers, P, are investigated and compared with those of LDED manufactured monolithic bulk metallic glass (BMG). Results show that both BMGCs have a multi-component microstructure that includes dual-sized Nb particles and devitrification-induced nano crystals at the melt-pool boundaries whereas the monolithic BMG contains only the latter. The nanocrystals at the melt-pool boundaries embrittle the LDED manufactured monolithic BMG, which reflects as a higher yield strength but negligible plastic deformation in uniaxial compression. In contrast, both BMGCs undergo significant plastic deformation as the Nb-reinforcements, besides improving plasticity by arresting propagating shear bands, reduces the enthalpy of relaxation, ΔHrel, of the matrix and decreases the volume fraction of the nanocrystallites, Vnc, at the melt-pool boundaries. However, amongst the two, the BMGC manufactured at higher P exhibits much higher shear band plasticity, despite having higher Vnc and lower ΔHrel. This is rationalized by analyzing the load transfer characteristics of the Nb-BMG matrix interfaces in the two BMGCs. [Display omitted] •LDED manufactured Nb-reinforced Zr-based BMGCs have significantly improved plasticity.•Nb induced plasticity improvement is achieved through limiting the structural relaxation of amorphous matrix.•Higher thermal diffusivity of Nb can minimize the devitrification induced brittle phases and thus enhance plasticity.•Partially dissolving Nb in the amorphous matrix by sufficient laser power can maximize shear band arresting capabilities.