New micro- and nanomechanical tests reveal the behavior of metal alloys at the micro- and nanoscale, but integrating these findings into engineering-scale metal-alloy designs and products remains a challenge.
“I can go and test a tiny volume of a metal to learn about how it behaves. This is very interesting because it gives us insight about some of the fundamental characteristics of material, because as you can imagine, if you are probing smaller and smaller volumes, then you look at simpler and simpler structures,” says C. Cem Taşan, associate professor of metallurgy.
“Still, at the macro world — the alloys, the materials that we all use — they have complicated microstructures. They are not simple at all,” he says. “The big challenge is, how do I connect the world of grains and atoms at the micro and nano scale to the deformations and crashes and impacts at the engineering macro scale.”
More than 50 students and professors from multiple departments and universities, as well as representatives from industry, participated in the third annual Alloy Design Workshop at MIT on Dec. 6. The workshop, titled “Micro-mechanics informed alloy design: Overcoming scale-transition challenges,” focused on bridging scale gaps, enabling complex alloy design through the understanding of fundamental nano-scale mechanisms of plasticity and fracture mechanics. This year’s workshop sponsors were Allegheny Technologies Incorporated (ATI) and ExxonMobil.
“There are specific challenges associated with carrying this information that is from the micro and nano scale to the engineering world, the scale you and I can see with our eye. That’s why we invited eight leading professors in the world to give talks,” Taşan says. The workshop ended with a panel discussion that included professors Timothy P. Weihs from Johns Hopkins University, Amy Clarke from Colorado School of Mines, Mitra Taheri from Johns Hopkins University, Sharvan Kumar from Brown University, Thomas Bieler from Michigan State University, and Motomichi Koyama from Tohoku University.
In her presentation, Clarke described her work studying solidification of materials such as aluminum-copper alloy melts. This real-time imaging with synchrotron X‐rays allows her to map out the processing space. These experiments also provide information that had been missing in aluminum copper alloy simulations, or models, she noted.
Humankind has been working metal for 4,000 years, mostly by trial-and-error up until the scientific age. “For some students, they may have the feeling maybe there isn’t so much new to be said in this field, a field that is thousands of years old,” Taşan observes. Yet, metals remain central to modern transportation, building, packaging, and many other key industries. “There is no projection I can think of in the near future where metals dominance in these structural applications is going to be significantly reduced,” Taşan notes. While newer composite materials may replace some metal components, “There is not a huge change coming, as we still need the properties metallic materials exhibit.”
Taşan noted what Apple Materials Engineering Director Jim Yurko spoke about in his recent Wulff lecture at MIT. “Why is a company that produces phones and computers interested in casting and heat treatment of aluminum alloys, to optimize their microstructure and precipitation?” Taşan asks. “Because they use aluminum and they need to somehow produce it, and solve the small problems with it. We do not always realize it, but metals are widely incorporated in most engineering products around us.”
“It’s very interesting that in this field — metallurgy and alloy design — challenges and solutions are distributed widely,” Taşan says. “In a single day, I may meet with a person from the jewelry industry and then somebody from the trucking or automotive industries. Very different materials, similar problems, and they all want solutions to their problems.”
Car and truck makers seek steel designs that are higher in strength, because stronger steel allows them to use less steel, which lightens vehicles and cuts fuel consumption. “But there is an interesting dilemma,” Taşan says. “Typically, if you make a material stronger, it becomes more susceptible to cracking and fracture. You can increase strength, but the more you increase strength, the less you can form complex shapes during manufacturing.
“This is an ongoing challenge. Researchers have been looking for different chemistries, different processing cycles, to be able to create microstructures that give both strength and ductility,” he says.
Taşan created the Alloy Design Workshops to emphasize the continued importance of alloy design in modern materials science. The workshop is held each year on the last day of the Materials Research Society Fall Meeting in Boston, Massachusetts, to provide an opportunity for the MIT community and the materials community as a whole to congregate in an intimate setting to present and discuss new, unpublished research.
Previous workshops covered the topics of “New guidelines in alloy design: From atomistic simulations to combinatorial metallurgy” and “Sustainability through alloy design: Challenges and opportunities.”