Discover the cutting-edge advancements in the field of Bulk Metallic Glasses (BMGs), also known as amorphous alloys, which are revolutionizing the manufacturing industry with their unique disordered atomic structure. These materials boast a range of exceptional properties, from high strength and fracture resistance to superior elasticity and corrosion resistance. Dive into the intricate world of Zr-based BMGs, their production through advanced injection molding techniques, and the fascinating microscopic world that reveals their internal structures and behaviors.
Bulk Metallic Glasses (BMGs) are a class of advanced materials that have garnered significant attention due to their amorphous atomic-scale structure. Unlike traditional crystalline metals, BMGs lack a long-range ordered pattern, which endows them with a combination of physical and mechanical properties that are highly desirable in various industrial applications. These properties include high strength, fracture toughness, an impressive elastic limit, and excellent wear and corrosion resistance (Huang et al., 2016; Trachenko, 2008).
Zirconium (Zr)-based BMGs are particularly notable for their superior Glass Forming Ability (GFA), allowing them to be processed into large parts exceeding several centimeters in thickness using conventional melting and casting methods (Liu et al., 2002). The net-shape as-cast form of BMGs offers reduced processing costs and enables the production of custom tools for a wide range of industries.
To successfully produce BMGs, cooling rates exceeding 10^3 K/s are required to prevent the formation of crystalline structures and maintain the amorphous microstructure during solidification (Huang et al., 2016; Petrescu et al., 2015). This rapid solidification is crucial in preserving the unique characteristics of BMGs.
The internal structure of BMGs is a key differentiator from conventional metals. While ordinary metals exhibit a periodic lattice, BMGs display a short-range organization typical of glass materials, including ceramics, polymers, and metals (Aversa et al., 2015; Petrescu et al., 2016).
Ion and electron microscopy techniques have been employed to conduct morphological microscopic observations of BMGs. These analyses reveal the presence of surface defects and crystalline phases, providing insights into the manufacturing process and the resulting material properties.
Differential Scanning Calorimetry (DSC) is used to analyze the calorimetric properties of BMG alloys. For instance, a Zr44Ti11Cu10Ni10Be25 alloy exhibits a glass transition between 380-395°C and multiple crystallization peaks, indicating the presence of different crystalline phases (Aversa and Apicella, 2016; Lewandowski et al., 2005).
Surface defects, such as grooves, can occur due to flow instabilities during the injection molding process. These defects are often filled with foreign materials, such as silicates, from the cutting process. The removal of these materials allows for a clearer understanding of the defect's origin (Mirsayar et al., 2016).
Microscopic observations aim to examine the arrangement of atoms and the presence of short-range order clusters. These clusters play a significant role in the material's properties and behavior during processing.
Energy Dispersive Spectrometry (EDS) is utilized to analyze the chemical composition of BMGs. The analysis reveals variations in the distribution of elements such as Zr, Ti, Cu, and Ni, which are influenced by the thermal and rheological behavior of the melt during injection molding. The presence of crystalline inclusions and their distribution within the material can be attributed to factors such as oxygen impurity, microalloying elements, and manufacturing process parameters (Liu et al., 2002).
The study of BMGs involves a deep understanding of material properties and the influence of manufacturing processes. The presence of crystalline phases and their distribution within BMGs can significantly affect the material's performance. Advanced microscopic techniques provide valuable insights into the internal structure and behavior of these materials, paving the way for further innovations in the field.
The authors express their gratitude to Liquid Metals Technologies Inc, California, USA, for providing the samples used in this research.
For a comprehensive list of references and further reading on the topic of Bulk Metallic Glasses and their properties, please refer to the original article and the cited works within.
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