Research on titanium alloys explores new concepts in materials science and engineering

Research on titanium alloys explores new concepts in materials science and engineering

Assistant Professor of Chemical and Materials Engineering Yufeng Zheng will begin research this August to design new titanium alloys with high strength and ductility (the ability of materials to bend and stretch without breaking). His work will potentially impact the design of new advanced light alloys for the aerospace and automotive industries, as well as promote electron microscopy training for undergraduate students with practical experience.

The five-year project is funded with a National Science Foundation CAREER Award of $ 520,583 received by Zheng earlier this year. The CAREER Awards are NSF’s most prestigious award recognizing early career faculty who have the potential to serve as academic role models in research and education and to guide progress in their department or organization’s mission. Zheng’s CAREER project, “Understanding the Role of Nanoprecipitates in Advanced Metastable Titanium Alloys,” seeks to design new titanium alloys using a new design strategy called metastability engineering.

“I will use metastable titanium alloys (titanium combined with other metallic elements and in an intermediate energy stage) as an example to study critical problems in metastability engineering,” said Zheng.

Metastability engineering, as Zheng explains, is a new concept in the design of advanced metal alloys capable of overcoming the trade-off between strength and ductility. Zheng in particular is studying the internal connections between the configuration of atoms in the nanoscale region in titanium alloys and the responses of these alloys to different external environments (such as different temperatures or load conditions) using the University’s state-of-the-art electron microscopes. .

It’s about titanium alloys

Titanium alloys – lightweight but strong, making them an ideal material for the aerospace and automotive industries – appear to be Zheng’s preferred material: in 2021, he received another NSF grant to research various titanium alloy compositions, including the use of alloying elements that cost less than those currently in use, as well as seeking strategies for producing titanium alloys at room temperature (another way to save on manufacturing costs).

This time around, Zheng is looking at titanium alloys as a way to study the new engineering concept of metastability. As he expresses it:

“In metastability engineering, the mass stability of alloys is adapted by optimizing their compositions to promote plastic deformation via deformation-induced transformation and other hardening mechanisms, such as precipitation hardening and solid solution hardening. and thus obtain the combination of excellent strength and ductility “.

And this is where nanoprecipitates – tiny precipitates undetectable by the human eye – come into play. Zheng’s CAREER Award project, “Understanding the Role of Nanoprecipitates in Advanced Metastable Titanium Alloys,” involves examining several metastable nanoprecipitates that form in titanium alloys, particularly the O ‘phase at the nanoscale, a new phase found and reported by Zheng for the first time in the world. As Zheng says:

“These metastable nanoprecipitates can alter the composition and structure in the local region at the nanoscale, and thus adapt the local stability in the metastable titanium alloys and enable the activation of phase transformations that are spatially limited only to the metastable regions at the nanoscale.” .

What is not fully understood, Zheng said, is the intrinsic correlation between metastable nanoprecipitates, local stability, and the confined phase transformation and deformation enabled in metastable titanium alloys.

“To fully understand the mechanisms that explain the high synergistic strength and ductility of metastable titanium alloys, there is a fundamental scientific need for a comprehensive understanding of the role of nanoprecipitates, such as the O ‘phase, in these alloys.” Zheng said.

Zheng adds that the information gleaned from this titanium alloy study could be applied to other advanced metallic materials, such as metastable steels and high entropy metastable alloys.

Small world

Electron microscopes play an important role in Zheng’s work: he is the acting director of the College of Engineering’s Electron Microscopy and Microanalysis Facility, which houses the operating system of the remote transmission electron microscope and the portable desktop scanning electron microscope. These electron microscopes are pivotal in materials science and engineering, enabling researchers to study the interrelationships between processing, structure and properties of materials at the micro and nanoscale.

They are also important for students.

“The use of microscopes in the classroom can help create a student-centered learning environment, stimulate students’ interests in materials science based on what they observe, and thus serve as an important strategy for inquiry-based education and on cases in education materials science, “says Zheng.

As part of his CAREER project, he plans to design new teaching modules on electron microscopy for the University’s graduate and undergraduate students, as well as outreach activities for K-12 students in the Reno community.

At the end of the five-year project, Zheng’s work could impact the industry as well. Titanium alloys with high strength and good ductility could improve light aircraft manufacturing for better fuel efficiency and CO reduction2 issue, Zheng predicts, among other industry applications.

Zheng acknowledges the support he has received from the Department of Chemical and Materials Engineering, the College of Engineering and Research and Innovation for his success, as well as from his students, including his Ph.D. student Dian Li; Colleagues; collaborators and friends.

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