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New Ti Alloy Database under Construction

Posted on: 10/09/2013
Researchers at The Ohio State University and their partners are building a database of new titanium alloys, using an innovative way to study metals. The goal of the project is to provide scientists with a guide that they can use to formulate titanium alloys for different applications, particularly for medical implants.

Project leader and TMS member Ji-Cheng (J.-C.) Zhao said that the $1 million grant his team has received from the National Science Foundation’s (NSF) Designing Materials to Revolutionize and Engineer our Future (DMREF) initiative will fund three years of research efforts and support graduate students on the project. This NSF program is part of the broader national Materials Genome Initiative announced by U.S. President Barack Obama two years ago.

Zhao and an another TMS member, Hamish Fraser, Ohio Eminent Scholar and professor of materials science and engineering at Ohio State, are collaborating with colleagues at Penn State to build the database, which will provide a reference guide to properties of alloys on the molecular scale.

“We need to know how much an alloy’s properties vary with composition,” said Zhao, also an Ohio State professor of materials science and engineering. “If we add a certain amount of molybdenum, and more or less niobium or tantalum to the titanium, what will happen? Will the alloy be stable? Will it be strong? We need to get that recipe.”

Plain titanium isn’t an ideal implant material, Zhao explained. Bones naturally flex to absorb some of the impact of movements. Titanium is less flexible, so wherever it connects to bone in the body, the titanium side of the connection flexes less than the bone. This stress and strain weakens the bone over time, and can break the connection to the implant—or break the bone itself. Yet, titanium is strong, nontoxic, and easy to work with, so it would be beneficial to determine how to increase its flexibility while retaining its more desirable qualities.

Zhao and his colleagues believe that adding bits of other chemical elements to titanium could create alloys that more closely match with bone. But which elements to add, and how much to add, are open questions.

To help determine these answers, Zhao will employ a technique that he invented more than a decade ago while working at General Electric. This involves placing small pieces of metal close together and heating them to high temperatures, so that atoms on the edges quickly diffuse to form just a sliver of alloy with a range of compositions between the metals. The sliver’s structure can be quite complex, depending on how many materials combine to form it and how wide a composition range it covers. Fraser will then use his expertise in microscopy to study the alloys’ structures on a molecular level, employing tools at Ohio State’s new Center for Electron Microscopy and Analysis. Zhao will complement these studies using ultrafast laser-based methods to probe the alloys’ properties.

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