Materials Performance

DEC 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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10 DECEMBER 2018 W W W.MATERIALSPERFORMANCE.COM Continued f rom page 9 UP FRONT ability to withstand forces under ultrahigh temperatures—is an important factor, since increased temperatures and pressures lead to creep deformation. In this study, the researchers assessed the alloy's creep in a stress range of 100 to 300 MPa for 400 h. Experiments were per- formed in a computer-controlled test rig under vacuum to prevent the material from oxidizing, or reacting with any potential air moisture, since this could ultimately lead to rusting. The researchers also report that, con- trary to prior studies, the MoSiBTiC alloy experiences larger elongation with decreas- ing forces. This behavior, they say, has so far only been observed with superplastic mate- rials that are capable of withstanding unex- pected premature failure. These findings are an important indica- tor for the alloy's applicability in systems that function at extremely high tempera- tures. The researchers say several additional microstructural analyses are needed to fully understand the alloy's mechanics and its ability to recover from exposure to high stresses. As such, the researchers hope to keep refining their findings. "Our ultimate goal is to invent a novel ultrahigh-temperature material superior to nickel-based superalloys and replace high- pressure turbine blades made of nickel- based superalloys with new turbine blades of our ultrahigh-temperature material," Yoshimi says. "To go there, as the next step, the oxidation resistance of the MoSiBTiC must be improved by alloy design without deteriorating its excellent mechanical prop- erties." For more information, visit www. First 3-D Image of Hydrogen-Induced Microscopic Crack In this study, cracks in a nickel alloy embrittled by hydrogen were caught as they propagated along grain boundaries. Image by Dharmesh Patel, Texas A&M University. A team of U.S. academic researchers has taken the first three-dimensional (3-D) image of a microscopic crack propagating through a metal damaged by hydrogen. Previously, the only way to analyze such a metal failure was to look at the separated pieces of a completely fractured compo- nent, which entails significant guesswork. The new research shows what is happening at the crack tip as a part begins to fracture. "It's much better than arriving at the crime scene after the fact," says Michael J. Demkowicz, a professor at the Materials Science and Engineering School at Texas

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