Characterization, mechanical properties and dimensional accuracy of a Zr-based bulk metallic glass manufactured via laser powder-bed fusion

Abstract

Bulk metallic glasses (BMGs) are high-strength, highly elastic materials due to their disordered atomic structure. Because BMGs require sufficiently high cooling rates to bypass crystallization, laser-based additive manufacturing (AM) methods have recently been employed for the fabrication of BMGs. In this study, we present an optimized Laser Powder-Bed Fusion (LPBF) process on a Zr-based BMG (Zr59.3Cu28.8Al10.4Nb1.5, in at.%), with a focus on characterization, mechanical properties, and dimensional accuracy. A volumetric density of 99.82% was achieved. Although the sample was qualified as amorphous via laboratory X-ray diffraction experiments, a more meticulous study using synchrotron radiation revealed nanocrystals in the heat-affected zones (HAZs) of the melt pool. Fast differential scanning calorimetry (FDSC) and numerical simulations were then employed to illustrate the mechanism of crystallization. The LPBF-processed alloy revealed excellent mechanical properties, such as high hardness, wear resistance, compressive strength, and flexural strength. Apart from vein-like patterns, the fracture surfaces of the compression test samples showed liquid-like features, which indicate a significant local temperature increase during fracture. The dimensional accuracy was assessed with a benchmark exhibiting complex geometrical features and reached at least 40 μm. The results indicate that LPBF processing is a promising route for the manufacturing of BMGs for various applications.

Keywords

• Additive manufacturing
• Bulk metallic glass
• Laser powder-bed fusion
• Nano-crystallization
• Precision manufacturing
• Selective laser melting