Atomic disorder and thermal stability in laser beam-shape-tailored 3D-Printed Zr-based bulk metallic glass under in-situ heating during high-energy X-ray diffraction

This study demonstrates that tailoring the laser beam intensity profile in laser powder-bed fusion (LPBF) significantly influences the thermal and mechanical behavior of Zr-based bulk metallic glasses (BMGs). Compared to the conventional Gaussian beam (GB), printing with a shaped beam (SB) profile leads to a less relaxed glassy structure, as evidenced by higher reduced mean atomic volume V(T), increased thermal expansion coefficient (αth), and greater equivalent configurational entropy (Seq). These features indicate enhanced resistance to structural aging upon heating. Although both GB and SB samples exhibit fully amorphous microstructures under X-ray diffraction, transmission electron microscopy reveals the presence of nanocrystals embedded within the amorphous matrix. Upon in-situ heating, synchrotron XRD shows that SB-printed samples undergo slower structural relaxation, supported by shifts in the pair distribution function and total structure factor. Furthermore, fluctuation electron microscopy identifies increased atomic-scale heterogeneity and medium-range order in SB-processed material. Mechanically, dynamic analysis reveals that the SB sample exhibits lower damping capacity, as shown by a reduced tan δ (loss modulus/storage modulus), indicating superior stability under dynamic loading conditions. Together, these results suggest that beam shaping in LPBF offers a powerful approach to tune the performance of metallic glasses by controlling their atomic structure and relaxation dynamics.