Atomic insights from molecular dynamics simulations into microstructure- dependent mechanical properties in Zr-based bulk metallic glass composites fabricated by LPBF

ZX Chang and GL Yao and YQ Ge, JOURNAL OF ALLOYS AND COMPOUNDS, 1042, 184073 (2025).

DOI: 10.1016/j.jallcom.2025.184073

Laser powder bed fusion (LPBF) enables the fabrication of Zr-based bulk metallic glasses (BMGs) with complex geometric structures, whereas crystallization within the heat-affected zone (HAZ) resulting from structural relaxation during multi-layer deposition in LPBF remains a critical challenge. Through molecular dynamics (MD) simulations of Zr- based BMGs fabricated by multi-layer LPBF, this study reveals the dynamic microstructural evolution of different nanozones. The results reveal a completely amorphous structure within the molten pool (MP). In contrast, crystallization occurs in the HAZ and remelted zone (RZ), as evidenced by significantly increased proportions of Voronoi polyhedrons (VPs) with characteristics of face-centered cubic (FCC) structure (<0,3,6,4 > and <0,4,4,6 >). The different amorphous/crystalline ratios within the microstructure generally tend to the elusive and complex deformation behavior and mechanism. Further MD simulations under tensile loading were performed to analyze the microstructure-dependent mechanical properties, the evolution of shear bands (SBs), and failure mechanisms of samples containing the MP of a fully amorphous structure and HAZs with different amorphous/crystalline ratios. The tensile simulations demonstrate that the high strength of the MP sample is attributed to its high proportion of mechanically stable 'Solid-like atoms' VPs. In contrast, these HAZ samples exhibit significant strain hardening and enhanced plasticity, stemming from extensive nucleation of new SBs and the formation of multiple SB networks, which delocalize plastic deformation and shift the deformation behavior from highly localized shear to more homogeneous plastic flow.

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