New titanium alloys combine strength and ductility, offering potential advancements for aerospace and biomedical industries.

In a breakthrough that could transform multiple industries, Massachusetts Institute of Technology researchers, in collaboration with ATI Specialty Materials, have developed new titanium alloys that break the conventional tradeoff between strength and ductility, potentially revolutionizing applications from aerospace to biomedical equipment.

Titanium alloys have long been valued for their exceptional mechanical properties, corrosion resistance, and light weight. However, optimizing these alloys often involves a tradeoff between two key characteristics – strength and ductility.

Stronger materials tend to be less deformable, while more deformable materials are typically mechanically weaker.

Now, researchers at MIT and ATI Specialty Materials have discovered an approach for creating new titanium alloys that defy this historical tradeoff.

By tailoring the chemical composition and lattice structure of the alloy and adjusting the processing techniques used, the team has developed alloys with exceptional combinations of strength and ductility.

Through careful selection of the alloying elements and their relative proportions, and of the way the material is processed, "you can create various different structures, and this creates a big playground for you to get good property combinations, both for cryogenic and elevated temperatures," said C. Cem Tasan, professor of metallurgy at MIT.

These findings, described in the journal Advanced Materials, highlight the new improvements achieved by the research team. The team discovered that by tailoring the chemical composition and lattice structure of the alloy while also adjusting the processing techniques, they could create titanium alloys with exceptional combinations of strength and ductility.

However, this assortment of possibilities requires a way to guide the selections and produce a material that meets specific application needs. The analysis and experimental results described in the new study provide that guidance.

The structure of titanium alloys, all the way down to the atomic scale, governs their properties, according to Tasan. Some titanium alloys are even more complex, made up of two different intermixed phases known as the alpha and beta phases – essentially two distinct atomic arrangements that can interact to enhance the alloy's overall performance.

In addition to selecting the right alloying elements, the processing techniques used play a crucial role. One such technique, called cross-rolling, emerged as a key factor in achieving the exceptional combination of strength and ductility.

Working alongside ATI researchers, the team tested various alloys under a scanning electron microscope while being deformed. This allowed them to observe how the microstructures responded to external mechanical loads.

They found a particular set of parameters – including composition, proportions, and processing method – that resulted in a structure where the alpha and beta phases shared deformation uniformly. This uniform deformation mitigates the tendency for cracking that typically occurs when the phases respond differently to stress.

"The phases deform in harmony," Tasan explained, yielding a superior material.

This collaboration involved a detailed analysis of the material's structure to understand the two phases and their morphologies. Local chemical analysis at the atomic scale was also conducted, and various techniques were used to quantify the material's properties across multiple length scales.

"We adopted a wide variety of techniques to quantify various properties of the material across multiple length scales," said Tasan. "When we look at the overall properties of the titanium alloys produced according to our system, the properties are really much better than comparable alloys."

This industry-supported academic research aimed at proving design principles for alloys that can be commercially produced at scale.

"What we do in this collaboration is really toward a fundamental understanding of crystal plasticity," said Tasan.

"We show that this design strategy is validated, and we show scientifically how it works," he added, noting that there remains significant room for further improvement.

For potential applications, the MIT professor said, "For any aerospace application where an improved combination of strength and ductility are useful, this kind of invention is providing new opportunities."