About this Abstract |
Meeting |
MS&T22: Materials Science & Technology
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Symposium
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Additive Manufacturing of Titanium-based Materials: Processing, Microstructure and Material Properties
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Presentation Title |
Transmission Electron Microscopy Analysis of Cellular Structure of Laser Processed Metastable Ti-Nb Alloy |
Author(s) |
Wenhao Lin, Eric Hoglund, Helge Heinrich, Ji Ma |
On-Site Speaker (Planned) |
Wenhao Lin |
Abstract Scope |
Laser powder bed fusion (LPBF) can promote novel microstructures. Because of the unstable BCC β phase, metastable titanium-niobium alloy after rapid solidification can generate uncommon local lattice distortions as well as several unexpected metastable phases. In this study, we perform line scans on a Ti-25 at% Nb substrate. Then transmission electron microscopy (TEM) samples are extracted across the melt pool boundary. Techniques such as SAED, HR(S)TEM, and 4D STEM are used for structure analysis. We found that the microstructure of the melt pool consists of nano-cells with an unusually large elastic strain field, sandwiched between nearly strain-free inter-cellular boundaries. Despite the inter-cellular regions remain as β phase, the lattice in the cells is an unfamiliar orthorhombic structure. Moreover, another uncommon o^' phase is also found in the melt pool at the room temperature. These results imply metastable β-Ti, unlike conventional alloys, appears to have a different response to thermal stress. |