Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA 18015, USA.
Department of Mechanical Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN 47803, USA.
Science. 2017 Oct 6;358(6359):97-101. doi: 10.1126/science.aam8256.
The properties of materials change, sometimes catastrophically, as alloying elements and impurities accumulate preferentially at grain boundaries. Studies of bicrystals show that regular atomic patterns often arise as a result of this solute segregation at high-symmetry boundaries, but it is not known whether superstructures exist at general grain boundaries in polycrystals. In bismuth-doped polycrystalline nickel, we found that ordered, segregation-induced grain boundary superstructures occur at randomly selected general grain boundaries, and that these reconstructions are driven by the orientation of the terminating grain surfaces rather than by lattice matching between grains. This discovery shows that adsorbate-induced superstructures are not limited to special grain boundaries but may exist at a variety of general grain boundaries, and hence they can affect the performance of polycrystalline engineering alloys.
随着合金元素和杂质优先在晶界聚集，材料的性能会发生变化，有时甚至是灾难性的变化。对双晶的研究表明，由于溶质在高对称性晶界上的偏析，通常会出现规则的原子图案，但在多晶中一般晶界是否存在超结构尚不清楚。在铋掺杂的多晶镍中，我们发现有序的、由偏析引起的晶界超结构出现在随机选择的一般晶界上，这些重构是由终止晶粒表面的取向驱动的，而不是由晶粒之间的晶格匹配驱动的。这一发现表明，吸附诱导的超结构并不局限于特殊的晶界，而是可能存在于各种一般晶界中，因此它们会影响多晶工程合金的性能。
