In a groundbreaking discovery that could revolutionize the field of materials science, researchers at the Massachusetts Institute of Technology (MIT) have developed a new method to create titanium alloys that are not only tougher but also more flexible than any previously developed. This innovative approach, which involves adjusting the chemical composition, lattice structure, and processing techniques, has resulted in a material with enhanced mechanical properties, potentially meeting the demands of aerospace and other applications.
Titanium alloys are indispensable structural materials in various fields, from aerospace and energy infrastructure to biomedical devices. However, like most metals, optimizing the performance of titanium alloys often requires a trade-off between two key characteristics: strength and ductility. Materials with higher strength tend to be less deformable, while those that are more easily deformed typically have lower mechanical strength.
Breaking the Trade-Off Barrier
Now, a collaborative effort between MIT researchers and scientists from ATI Specialty Materials has uncovered a method to produce a new type of titanium alloy that transcends this historical trade-off, resulting in a material that combines both strength and ductility. This breakthrough could pave the way for new applications and advancements in various industries.
The research findings, published in the journal Advanced Materials, include contributions from Shaolou Wei (ScD ’22), C. Cem Tasan, a professor at MIT, postdoctoral associate Kyung-Shik Kim, and John Foltz from ATI Specialty Materials. The team’s improvements stem from customizing the alloy’s chemical composition and lattice structure, along with adjusting the processing techniques used for industrial production.
Titanium alloys are valued for their superior mechanical properties, corrosion resistance, and lightweight characteristics. By carefully selecting alloy elements and their relative proportions, as well as the material’s processing methods, you can create a variety of different structures, which provides a large stage for obtaining good combinations of properties, whether at low or high temperatures, Tasan explained. However, the numerous possibilities require a method to guide selection to produce materials that meet specific application needs, which the new research aims to provide.
The Structure Determines the Properties
The structure of titanium alloys, down to the atomic scale, dictates their characteristics. In some titanium alloys, this structure is even more complex, consisting of two different phases: the alpha (α) phase and the beta (β) phase. The key strategy of this design method is to consider different scales, Tasan noted. One scale is the structure of individual crystals. For instance, by carefully selecting alloy elements, you can obtain a more desirable α-phase crystal structure, thereby achieving specific deformation mechanisms. The other scale is the polycrystalline scale, involving the interaction between the α and β phases.
Cross-Rolling: A Key Technology for Enhanced Performance
In addition to selecting the right alloy materials and proportions, the processing steps also play a crucial role. The research team discovered that a technique known as cross-rolling is another key to achieving the perfect combination of strength and ductility.
Collaborating with ATI researchers, the team tested various alloys under deformation in a scanning electron microscope, revealing the details of the alloy’s microstructure response to external mechanical loads. They found that a specific set of parameters—composition, proportion, and processing methods—can produce a structure where the α and β phases share deformation uniformly, reducing the tendency for cracking when the two phases react differently. Tasan stated, The phases deform harmoniously.
This cooperative response to deformation can result in a high-quality material. We studied the structure of the materials to understand these two phases and their morphology, and we studied their chemical nature through local chemical analysis at the atomic scale. We employed various techniques to quantify the material’s properties at multiple length scales, Tasan said. When we observed the overall characteristics of the titanium alloys produced according to their system, their properties were indeed much better than those of similar alloys.
A Step Towards Commercialization
This academic research, supported by the industry, aims to demonstrate the design principles of alloys that can be produced on a large scale for commercial purposes. Tasan noted, The work we did in this collaboration was actually to fundamentally understand crystal plasticity. We demonstrated that this design strategy is effective and showcased from a scientific perspective how it works. As for the potential applications of these research findings, this invention provides new opportunities for any aerospace application that benefits from an improved combination of strength and ductility.
The implications of this research are significant, offering a promising future for materials science and engineering. The development of these new titanium alloys could lead to advancements in various industries, from aerospace to medical devices, where strength and flexibility are crucial.
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