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Effect of pre-existing nuclei on crystallization during laser welding of Zr-based metallic glass
摘要： In this study, experiments are carried out in laser welding of a Zr-based (Zr52.5Ti5Al10Ni14Cu17.9) bulk metallic glass (BMG), pre-existing nuclei nucleus density has significant influence on its crystallization behavior. Based on the classical nucleation/growth theory, it is concluded that a small amount of pre-existing nuclei in a BMG can shift the time-temperature-transformation (TTT) curve from a well-known ‘C-shape’ to a ‘ε-shape.’ This result provides fundamental understanding on why the shape of the TTT curve for a heating process is different from that for a cooling process for the same BMG. Two quality factors were defined as a measure of the effect of pre-existing nucleus density. By integrating the classical nucleation/growth theory with the heat transfer model, the evolution of crystalline phase during laser welding for a BMG with pre-existing nuclei was studied, and the modeling predictions compared favorably with the experimental results.
关键词： Crystallization,Nucleation and growth,Laser processing,Metallic glasses,Amorphous alloys
更新于2025-11-28 14:24:20
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Preparation of Fe-Co-B-Si-Nb bulk metallic glasses by laser powder bed fusion: Microstructure and properties
摘要： In this work, laser powder bed fusion (LPBF) was employed for the preparation of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 bulk metallic glasses (BMGs). Microstructural evolution, thermal stability and mechanical properties of LPBF-processed samples using different laser power and scanning speed were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA), electron backscatter diffraction (EBSD), differential scanning calorimetry (DSC) and nanoindentation. The results show that low area energy input facilitates the formation of Fe-Co-B-Si-Nb BMGs with a large amorphous fraction. LPBF-processed sample with an area energy density of 1.25 J/mm2 (at a laser power of 60 W and a scanning speed of 600 mm/s) exhibits a nearly fully glassy microstructure with an amorphous fraction of approximately 99%, meanwhile identical characteristic properties of LPBF-processed samples are correlated with the processing parameters during LPBF. This work demonstrates that LPBF is a promising method to prepare fully amorphous Fe-Co-B-Si-Nb BMGs. The results provide key insights for the fabrication of BMGs and BMGs composites with the desired microstructure possessing almost and properties by additive manufacturing.
关键词： Bulk metallic glasses,Laser powder bed fusion,Amorphous fraction,Crystallization,Microstructure,Nanoindentation
更新于2025-09-23 15:19:57
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A Study of Structure and Morphology of Bulk Metallic Glasses after Laser Beam Treatment
摘要： Recently, the Zr-based bulk metallic glasses (BMGs) have attracted attention because of their good glass-forming ability and excellent mechanical properties. The amorphous structure is thermodynamically unstable, and it tends to change into an equilibrium crystalline state. The objective of this work is to test the influence of the laser beam on the surface structure and morphology of BMGs with zirconium matrix. The material for the examination was Zr55Cu30Ni5Al10 alloy obtained by high-pressure copper mold casting method in the form of a plate in specified dimensions. In this paper, irradiation with single impulse and laser beam welding emitted in a pulsed mode which consists of a series of overlapping point interactions were used. Different parameters of the laser beam were employed. Microscopic observations proved that after laser treatment amorphous-crystalline structure appears in the heat-affected zone (HAZ). High-resolution transmission electron microscopy analysis of irradiated metallic glass showed that small amount of crystalline Zr2Ni-type phase was produced in the HAZ, whereas in the fusion zone and parent material amorphous structure appears. What is more, it has been observed that the higher laser beam frequency and energy the more weld penetration takes the shape of an ellipse.
关键词： Zr-based alloy,bulk metallic glasses,laser melting,surface morphology
更新于2025-09-12 10:27:22
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High-throughput screening of laser additive manufactured metallic glass via ultrasonic wave
摘要： Laser additive manufacturing (LAM) technology provides an opportunity to fabricate bulk metallic glasses (BMGs) without any dimensional constraint and achieve the large-scale applications of BMGs. However, flaws, such as cracks, gas porosity, and crystalline phases, are always formed accompanied by the process of LAM, which seriously worsens the mechanical and physical properties of the resulting BMGs. Here, we present a novel method that involves ultrasonic wave technique to high-throughput screen the optimum process parameters for the LAM of BMG. A parameter library, constituted by a series of rectangular BMG samples, is rapidly fabricated by the LAM method under continuously changed combinations of laser power and travel speed. the ultrasonic attenuation factor, which is sensitive to the flaws, is used as the monitor to screen the parameters of the BMGs fabricated by the LAM. Using this approach, the laser power of 1300 W and travel speed of 600 mm/min are estimated as the optimum parameter combination for the LAM of a Zr51ti5ni10cu25Al9 (Zr51) BMG with the slightest flaws. The amorphous-phase dominated microstructure and the sufficiently high tensile strength of the subsequent fabricated large-sized Zr51 BMG sample verify this optimum parameter combination.
关键词： High-throughput screening,Bulk metallic glasses,Ultrasonic wave testing,Optimum process parameters,Laser additive manufacturing
更新于2025-09-11 14:15:04