Microscale elastoplastic deformation of a Zr-based bulk metallic glass fabricated by laser powder bed fusion: Strain analysis by high-energy X-ray diffraction

The fabrication of bulk metallic glasses (BMGs) by additive manufacturing has finally overcome the size constraint characterizing glass formation using casting. Unfortunately, BMGs synthesized by additive manufacturing, such as laser powder bed fusion (LPBF), show degraded mechanical properties compared to the cast counterparts, which are typically ascribed to defects, such as pores. Here, to explore the influence of the local structural conditions generated by LPBF processing, we analyze the microscale elastoplastic deformation of a Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 BMG fabricated by LPBF and casting using high-energy X-ray diffraction. Our results show that the Poisson´s ratio of the LPBF BMG is lower than the cast counterpart, which explains the reduced plasticity of this material. The smaller Poisson´s ratio also reduces the energy barriers for STZ activation. Lower barriers imply that STZ activation in the LPBF glass is reached at lower stresses, explaining the lower yield strength. The strain map across a shear band in the LPBF BMG shows the same characteristics already observed in the cast material, implying that the same mechanism of shear band nucleation and propagation acts in both specimens; this offers the possibility to extend the existing ductilization strategies found effective in cast BMGs to the corresponding LPBF specimens.