The difference in microstructure between Liquidmetal alloy and other materials may be the most underappreciated difference between Liquidmetal alloy components and products manufactured with other techniques such as metal injection molding (MIM) or additive manufacturing (AKA “3D Printing”).
If you have studied our website or have researched “bulk metallic glass”, you have likely seen an illustration of randomly distributed circles against a white background representing the liquid-like microstructure of Liquidmetal alloys. It is this random atomic structure that fundamentally enables the material properties and process advantages of our alloys. For more background and a history of bulk metallic glasses, please download our Liquidmetal whitepaper.
To be clear, Liquidmetal alloys are not liquid at room temperature. We heat the alloy until it is liquid and its viscosity is low enough to facilitate injection. We then inject the molten alloy into permanent steel molds. In the mold, the Liquidmetal alloys are cooled rapidly enough to freeze in its amorphous state, acquiring full strength and other capabilities in one-step; there are no debinding, sintering or polishing steps after molding which greatly simplifies the process. An animated diagram of the injection molding process can be found in our recent blog article.
In our quest to further educate and support the development of commercial bulk metallic glasses, we wanted to share images we rarely shared in the past: what do Liquidmetal alloys’ microstructure actually look like up close and personal? If you are a metallurgist, the images may look boring: no beautifully polarizable phases, complex angular patterns, no organic looking dendrites, or wonderfully oriented precipitates. However, it is this remarkable uniformity that makes Liquidmetal parts so uniformly flawless, repeatable, and strong.
Here are images of actual parts in a direct side-by-side comparison of microstructure between MIM, Additive Manufacturing, and Liquidmetal alloys.
The images above were created by cutting through the middle of a part, mounting the part in a hard epoxy, and then polishing the cross-section to a very, very fine finish. Once polished, the microstructures can be observed by means of optical microscopy, using polarizing filters to bring out the crystalline structure.
As you can see, the MIM cross-section reveals the process used to manufacture the part (involving many grains of microscopic particles being fused together). The additive manufactured part (3D printed) reveals a more uniform but also grainy structure that is generated as the metal particles are successively heated and cooled layer-by-layer via laser sintering. In contrast, the Liquidmetal polished cross-section is completely uniform in structure, having the same properties everywhere in the part, down to nanometer length scales.
Because Liquidmetal alloys do not have grains (which can be points of weakness), parts produced with our alloy have a unique combination of elastic performance and high tensile strength. Previously only low strength materials like plastics had high elastic strain limits as seen in this graph. If you missed our 1st Application Note blog video, here is a quick 2-minute video demonstrating how elastic (i.e., how much force/stress can be applied without damage) Liquidmetal alloy products behave in real-life tests and applications.