Radiotracer investigation of silver grain boundary diffusion and segregation in copper bicrystals at low temperatures: the direct determination of grain boundary diffusion coefficients

本项目致力于银在铜双晶中晶界扩散的实验研究。将对Σ5附近的双晶进行精确表征。我们最近提高了放射性示踪剂测量的灵敏度和精确度，从而首次在如此低的温度下确定了双晶中的晶界扩散，从而满足了所谓的C型动力学条件。这些测量将直接提供溶质晶界扩散系数DGB的值，这是迄今为止在双晶中从未测量过的。在较高的温度下，测量将按照所谓的B型动力学进行，该动力学产生三倍积值，P=S·δ·dgb，其中S是偏析因子，±晶界宽度。将沿取向双晶倾斜轴和垂直于取向双晶倾斜轴的低温和高温测量相结合是项目的关键，首次确定了产物S·δ及其可能的各向异性。目前对晶界扩散和偏析现象的认识可望因此而得到相当大的改善，因为它是迄今为止唯一的研究。

The project is focused on the experimental investigation of grain boundary diffusion of Ag in Cu bicrystals. Precisely characterized near Σ5 bicrystals will be investigated. We have recently improved the sensitivity and precision of the radiotracer measurements so that, for the first time, grain boundary diffusion in a bicrystal will be determined at such low temperatures that the so-called C-type kinetic conditions will be satisfied. These measurements will provide directly the values of the solute grain boundary diffusion coefficients, Dgb, which were never measured so far in bicrystals. At higher temperatures the measurements will be performed in the so-called B-type kinetics, which yield the triple product values, , P = s • δ • Dgb, where s is the segregation factor and ± the grain boundary width. The combination the low- and high-temperature measurements performed both along and perpendicular to the tilt axis of the oriented bicrystal is the key of the project and the product s • δ and its probable anisotropy will be determined for the first time. Considerable improvement of the current understanding of grain boundary diffusion and segregation phenomena is expected from this in its completeness so far unique investigation.