In the wee hours of a Saturday morning, Professor of Materials Science and Engineering Tony Rollett and graduate students Ross Cunningham and Tugce Ozturk sit in Sector 2 of the mile-wide Advanced Photon Source at the Argonne National Laboratory in Chicago, Illinois. In front of them is an enormous synchrotron x-ray machine, powerful enough to see through heavy metals down to one millionth of a meter, roughly one hundredth of a human hair. The unique equipment is in such high demand that the team has just forty-eight hours to use the x-rays before they must pack up and carry their data back to Pittsburgh.
Scientists who are able to secure time with the synchrotron study the internal structure of materials including polymers, biomedical biopsies, and alloys. The synchrotron takes detailed, 3-D images that are used to characterize materials. The images are so precise that researchers often turn to synchrotron technology to identify ancient insect fossils, which can barely be seen under a microscope. Instead of leveraging this powerful technology to learn about ancient materials, Rollett’s group seeks to gain elusive information about 3-D printed metals.
By looking deep inside thin slices of 3-D printed titanium parts, the group examined defects in the printed metal that are difficult to detect even with current laboratory-grade equipment. These defects, called pores, make the part more susceptible to breakage when the part is exposed to repeated weight or stress. Potential for breakage might not be a big deal for your 3-D printed toothbrush holder, but it is significantly more important when it comes to a 3-D printed part for a jet engine.
We are one of the only universities chasing after advanced characterization techniques in the metals 3-D printing space.Tony Rollett, Professor, Materials Science and Engineering, Carnegie Mellon University
Although 3-D printing, or additive manufacturing, is currently used for rapid prototyping, it may become the mainstream manufacturing process for grander applications such as aerospace parts, custom biomedical implants, and high performance automobiles.
Improving the internal structure of 3-D printed metal parts is a challenge that must be met in order for this manufacturing process to become more mainstream. Rollett’s team published a paper in the Journal of Minerals, Metals, and Materials Society in collaboration with Professor of Mechanical Engineering Jack Beuth, which showed that a majority of the porosity in 3-D printed titanium could be eliminated by making adjustments to the process parameters of the machine. Less porosity means stronger, more reliable end-parts.
“Having a strong understanding of the fundamental science of additive manufacturing materials is necessary in order to use them in aerospace and other demanding applications,” says Beuth. “The ability to visualize porosity and flaws in 3-D with such high precision is a breakthrough capability in additive research.”
Rollett and his team plan to continue their research to determine if it is possible to eliminate all remaining porosity from 3-D printed titanium and other metals. This is an important goal because it is currently thought that some amount of porosity will always exist in 3-D printed materials.
“In a conventional material like steel, there aren’t any of these pores,” says Rollett. “In additive manufacturing materials, there they [pores] are. You have to figure out how to understand them and deal with them. It is a new challenge in the field of materials science.”
Carnegie Mellon’s NextManufacturing Center, where Beuth serves as director and Rollett as associate director, has focused its attention on materials science projects like this one. As one of the world’s leading research centers for additive manufacturing, the center is advancing the field of additive manufacturing by meeting the research challenges of the industry.