b'Look-AheadTHE TOUGHEST MATERIAL ON EARTHS cientistshavemeasuredthecompromise between these prop- create, George foresees uses in sit-highesttoughnesseverre- erties. But this material is both, anduations in which environmental ex-corded of any material while inves- instead of becoming brittle at lowtremes could destroy standard me-tigating a metallic alloy made oftemperatures, it gets tougher. tallic alloys, such as in the frigid tem-chromium, cobalt and nickel. TheThe toughness of this materialperatures of deep space. He and his metal is extremely ductile, whichnear liquid helium temperatures (20team at ORNL also are investigating in materials science means highlykelvin, -424 Fahrenheit) is as high ashow alloys made of more abundant, malleable, and impressively strong,500 megapascals square root me- less expensive elementsthere meaning that the metal resists per- ters, said research co-leader Rob- is a global shortage of cobalt and manent deformation. The strengthert Ritchie, senior faculty scientistnickel due to their demand in the and ductility of the metal also im- at Berkeley Labs materials sciencesbattery industrycould be coaxed prove as it becomes colder. Thisdivision and Chua professor of en- into having similar properties.runs counter to most other materi- gineering at University of Califor- Theprogressisexciting,but als in existence. nia, Berkeley. In the same units,Ritchie warns that real-world use The team was led by researchersthe toughness of a piece of silicon iscould be a ways off for good reason.from Lawrence Berkeley Nationalone, the aluminum airframe in pas- When you are flying on an air-Laboratory and Oak Ridge Nationalsenger airplanes is about 35, andplane, would you like to know that Laboratory. the toughness of some of the bestwhat saves you from falling 40,000 When you design structural ma- steels is around 100. So 500, its afeet is an airframe alloy that was terials, you want them to be strongstaggering number. only developed a few months ago? but also ductile and resistant toNow that the inner workings ofhe said. Or would you want the ma-fracture, said project co-lead Easothe CrCoNi alloy are better under- terials to be mature and well under-George, the governors chair forstood, it and other high-entropy al- stood? Thats why structural mate-advancedalloytheoryandde- loys are one step closer to adoptionrials can take many years, even de-velopment at ORNL and Univer- for special applications. Althoughcades, to get into real use.CTEsity of Tennessee. Typically, its athese materials are expensive toAliyah KovnerMicroscopy-generated images show the path of a fracture and accompanying crystal structure deformation in the CrCoNi alloy at nanometer scale during stress testing at 20 K (-424 F). The fracture is propagating from left to right.R. Ritchie/Lawrence Berkeley National Laboratoryctemag.com/cteguide.com61LookAhead.indd 61 3/17/23 9:36 AM'