Characterising 3D-Printed metallic glasses : Unlocking performance through microstructure in additive manufacturing

Additive manufacturing is gaining its popularity as a powerful tool for producing components with complex geometries. To fully harness the potential of this technology, a thorough understanding of the resulting material's characteristics is not just beneficial, it's essential. This article by our R&D engineer team delves into the essential techniques used to characterise 3D-printed metallic glasses, demonstrating how we connect microstructure – the material's fundamental architecture – to achieve desired implant performance. We'll also showcase insights from groundbreaking research on optimising these materials, drawing upon the study "Quantifying chemical homogeneity across the melt pool in laser powder-bed fusion of metallic glass matrix composites from blended elemental powders" by Wannapraphai et al. highlighting the crucial link between processing and material properties.

The importance of microstructure

The microstructure of a material – its arrangement of phases, grains, and other features at a microscopic level – dictates its mechanical properties, corrosion resistance, and biocompatibility. As highlighted by Gregg Olson's work, microstructure and processing is a critical factor in determining a material's overall performance. In 3D-printed metallic glass, achieving a controlled microstructure is paramount for implant success.

• Phase Composition: The presence and distribution of different phases (e.g., amorphous matrix, crystalline reinforcement) influence strength, toughness, and elasticity.

• Chemical Homogeneity: A Uniform distribution of elements is essential to avoid weak points and ensure consistent performance.

• Defect Control: Porosity and cracks can compromise structural integrity and must be minimised.

Key Characterisation Techniques

We use a range of techniques to analyze the microstructure of 3D-printed metallic glasses:

• X-ray Diffraction (XRD): This technique identifies the amorphous and crystalline phases present in the material. In the context of the featured research, XRD was used to confirm the formation of specific phases like amorphous, β−(Ti,Zr) and (Ti,Zr)2​Cu in the Ti-Zr-Cu system.

• Scanning Electron Microscopy (SEM): SEM provides high-resolution images of the material's microstructure, revealing features like melting region, phase distribution, and porosity. The research by Wannapraphai et al. utilised SEM to observe the melt pool geometry and microstructural evolution under different processing conditions.

• Energy-Dispersive X-ray Spectroscopy (EDX): EDX is used in conjunction with SEM to analyse the elemental composition and distribution within the microstructure. This technique helps to assess chemical homogeneity, as demonstrated in the featured study where EPMA, a similar and highly sensitive technique, generates detailed chemical maps, visually demonstrating how elemental distribution varies with processing parameters.

• Scanning Transmission Electron Microscopy (STEM): STEM provides atomic-scale imaging and analysis, allowing for detailed investigation of phase interfaces and nanoscale features. In the research, STEM-EDX was used to confirm the presence of amorphous regions within the metallic glass matrix composite (MGMCs), a key characteristic of these materials.

• Vickers Hardness Testing: This technique measures the material's resistance to indentation, providing an indication of its strength. The study correlated hardness measurements with microstructural features to evaluate the effect of processing parameters on the material's mechanical properties.

This work also collaborates with leading academic institutions such as Chulalongkorn University, Queen Mary University of London, University of Cambridge, and University of Oxford to further advance the field of 3D-printed metallic glasses.

Learn more and share your thoughts about the laser powder-bed fusion of metallic glass by Wannapraphai et al, https://doi.org/10.1016/j.jmrt.2025.02.204. We encourage you to delve into the full research paper for a comprehensive understanding of these exciting developments.