b'Look-AheadMAKING TURBINES MORE EFFICIENTM etals containing niobium sili-cide are promising materials that can withstand high temper-atures and improve efficiency of gas turbines in power plants and aircraft. But it has been difficult to accurately determine mechanical properties of these metals due to their complex crystal structures.Scientists at Kyoto University in Japan now have measured what happens at the microlevel when pressure is applied to tiny samples of these materials. The approach, which was published in the jour-nal Science and Technology of Ad-vanced Materials, could help scien-tists obtain the accurate measure-ments needed to understand the atomic-level behavior of complex crystals and develop more heat-tol-erant components for gas turbines.Our results demonstrate the cut-ting edge of research into plastic deformation behavior in crystalline materials, said study correspond-ing author Kyosuke Kishida.Plastic deformation describes the distortion that occurs at the atomic level when a sustained forceShown are scanning electron microscopy secondary electron images of deformed is applied to a crystal. This is diffi- micropillar specimens with the four loading axis orientations tested in the study.cult to measure in complex crystals. He and his colleagues have beenusing scanning electron microscopy-Nb Si , Kishida said, which is in 5 3using a new approach to systemati- on the samples before and after themarked contrast to Mo 5 SiB 2 .cally measure plastic deformation intest, scientists were able to detectThis could mean that -Nb Siis 5 3crystals showing promise for use inthe planes and directions in whichat a disadvantage compared with high-temperature gas turbines. deformation took place. This was fol- Mo 5 SiB 2for use as a strengthening Researchersmeasuredplasticlowed by simulation studies basedcomponent in metal-based alloys. deformation in a niobium silicideon theoretical calculations to furtherHowever, he and his team think that called-Nb SiTiny micropillarsunderstand what was happening atthe inherent brittleness of this ma-5 3.of these crystals were exposed tothe atomic level. Finally, the teamterial could be improved by adding very small amounts of stress using acompared the results with those of aother alloying elements.machine with a flat-punch indenterboron-containing molybdenum sili- The team plans to use the ap-at its end. The stress was appliedcide, or Mo 5 SiB 2 , that the research- proach to study mechanical prop-to different faces of the sample toers previously had examined. erties of other crystalline materials determine where and how plasticWe found that instantaneouswith complex structures.CTEdeformation occurs in the crystal. Byfailureoccursrathereasilyin ResearchSEActemag.com/cteguide.com45LookAhead.indd 45 5/14/21 2:39 PM'