Connecting micro and nano scale mechanics to real world alloy design.
|Previous Alloy Design Workshop participants with the MIT dome in the background. This year’s workshop, “Micro-mechanics informed alloy design: overcoming scale-transition challenges,” will take place on Friday, Dec. 6, 2019, in MIT Building 6, Room 104 (Chipman). Image courtesy of C. Cem Taşan.|
New micro- and nano-mechanical tests reveal the behavior of metal alloys at the micro- and nano-scale, but integrating these findings into human scale metal alloy designs and products remains a challenge.
“I can go and pick up a tiny volume of the material and test it and 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 atoms and grains at the micro and nano scale to the world of deformations and crashes and impacts.”
The “Micro-mechanics informed alloy design: overcoming scale-transition challenges” workshop will tackle the problem of connecting the information learned at the small scale to the macro world on Friday, Dec. 6, 2019, from 8 a.m. to 5 p.m. in MIT Building 6, Room 104 (Chipman). The workshop, which is the third annual Alloy Design Workshop at MIT, is open to researchers from outside MIT, as well as the MIT community, but registration is required by Monday, Dec. 2, 2019. This year’s workshop sponsors are Allegheny Technologies Incorporated (ATI) and Exxon Mobil.
“There are specific challenges associated with carrying this information that is from the micro and nano scale to the engineering world, the millimeter scale, 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 will conclude with a panel discussion.
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 and computing. “There is no projection I can think of in the near future where metals dominance in these structural applications is going to be reduced,” Taşan notes. While newer composite materials may nibble around the edges, replacing some metal components, “There is not a huge change coming, so we still need metallic material around.”
Taşan noted that in Apple Materials Engineering Director Jim Yurko’s recent Wulff lecture at MIT, Yurko spoke about casting of aluminum alloys, heat treatment, and optimization of their microstructure and precipitation. “Why?” Taşan asks, “because they use aluminum and they need to somehow produce it, and solve the small problems with it.”
Widely distributed solutions
“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.”
|Associate Professor of Metallurgy C. Cem Taşan. Image, Lillie Paquette, MIT School of Engineering.|
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 shape something, deform something.
“People have been looking for different chemistries, different processing cycles, to be able to create microstructures that give both strength and ductility,” he says.
In his own research, to come up with a less brittle steel alloy, Taşan and colleagues in Germany and Japan took a cue from bone, which naturally combines strength and light weight through a lattice-like internal structure made up of open spaces and connections at many different length scales. They devised a laminated steel nanostructure that reduces fatigue and gives the steel a fracture resistance similar to that of bone under repeated stress.
Taşan also discovered a new way to study an effect known as hydrogen embrittlement, which is caused by hydrogen atoms penetrating into, and weakening, a metal alloy. The new technique studies hydrogen penetration by placing the metal alloy in a liquid electrolyte inside a well-sealed chamber and scanning it with an electron beam. Taşan’s research showed this technique reveals the effects of hydrogen atoms on the structure of the metal.
Prof. 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 (MRS) Fall Meeting in Boston 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.”