b'Look-AheadFINE-TUNING ALLOYS FOR HIGH TEMPSS uperalloysthatwithstandex- effect, promises to advance the de- Vitos said these new findings help tremely high temperatures soonsign of high-temperature alloys withexplain the peculiar high-temper-could be tuned even more finely forexceptional mechanical stability.ature properties of special alloys specific properties, such as mechani- The research team was led by himused in jet engines, such as nickel-cal strength, as a result of new findings. and composed of KTH Royal In- base superalloys.A phenomenon related to thestitute of Technology researchersInvar has two known effects: ther-invar effectwhich enables mag- Zhihua Dong, Wei Li and Stephanmal expansion and elasticityfor neticmaterialslikenickel-ironSchnecker. instance, the ability to spring back after bending. Because both Our findings create a new platform for tailoringeffects are linked to the in-high-temperature properties of technologicallyterplay between temperature and magnetic order, they are relevant materials toward plastic stabilityconsidered to be specific to at elevated temperatures. magnetically ordered alloys.Using first-principles quan-tum mechanical modeling, theresearchersidentified how invariant plasticity also occurs in nonmagnetic alloys when a structural balance ex-ists at the atomic level be-tween cubic and hexagonal close-packed structures.Thenewdiscoveries emerged from a long-term collaboration with industry to find alternatives to carcino-genic cobalt in hard metals, such as cutting tools. Vitos said the revelations broaden the palette of invar phenom-ena and material composi-tions, with clear implications for new applications.L. Vitos Our findings create a new A piece of alloy is stress-tested at a lab at KTH Royal Institute of Technology. platform for tailoring high-tem-perature properties of techno-alloys to keep from expanding withShort for invariant, invar plastic- logically relevant materials toward increasing temperaturewas re- ity allows magnetically disorderedplastic stability at elevated tempera-ported to have been discovered innickel-iron alloys to show practicallytures, he said.paramagnetic, or weakly magne- invariant deformation behavior overThe research was supported by tized, high-temperature alloys. a wide temperature range, makingthe Swedish Research Council, the Levente Vitos, professor at KTHthem ideal for turbines and otherSwedish Foundation for Strategic Royal Institute of Technology inmechanical uses in extremely highResearch and the Swedish Founda-Stockholm, said the breakthroughtemperatures. tion for International Cooperation in research, which includes a generalThe invar effect, however, neverResearch and Higher Education.CTEtheory explaining the new invarhas been fully understood, and David Callahanctemag.com/cteguide.com41LookAhead.indd 41 7/20/21 9:39 AM'