Abstract
The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations. Examples are shape memory alloys and high strength steels, which together stand for 1,500 million tons annual production. In these materials, martensite formation and mechanical twinning are tuned via composition adjustment for realizing complex microstructures and beneficial mechanical properties. Here we report a new phase transformation that has the potential to widen the application window of Ti alloys, the most important structural material in aerospace design, by nanostructuring them via complexion-mediated transformation. This is a reversible martensitic transformation mechanism that leads to a final nanolaminate structure of α″ (orthorhombic) martensite bounded with planar complexions of athermal ω (a–ω, hexagonal). Both phases are crystallographically related to the parent β (BCC) matrix. As expected from a planar complexion, the a–ω is stable only at the hetero-interface.
Highlights
The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations
This system is a variation of the gum metal[2], which has drawn significant interest due to its unusual mechanical properties and various deformation mechanisms that have been controversially reported as possible underlying reasons for such behaviour
The new a–o planar complexion observed in this study is induced by a diffusionless martensitic transformation (b-a00), that is, it forms through a diffusionless process
Summary
The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations. We report a new phase transformation that has the potential to widen the application window of Ti alloys, the most important structural material in aerospace design, by nanostructuring them via complexion-mediated transformation This is a reversible martensitic transformation mechanism that leads to a final nanolaminate structure of a00 (orthorhombic) martensite bounded with planar complexions of athermal o (a–o, hexagonal). The observed mechanism involves a so far undiscovered coupling of several athermal phase transition steps at the interface, namely, b-a00 martensitic phase transformation and b-a–o transition, creating planar complexions at the a00/b interfaces as well as nano-layered martensitic twinning (Fig. 1) It results in a final nanolaminate composite microstructure throughout the bulk Ti gum metal. It forms from the b-matrix to accommodate the interfacial strain of a00/b-phase boundaries during b-a00 martensitic transition and further mediates the transition by influencing the twinning mode, and results in a final nanolaminate composite microstructure throughout the bulk Ti alloy on cooling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
