Boll T, Al-Kassab T, Yuan Y, Liu Z G
Institut für Materialphysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany.
Ultramicroscopy. 2007 Sep;107(9):796-801. doi: 10.1016/j.ultramic.2007.02.011. Epub 2007 Feb 28.
Dual-phase TiAl/Ti3Al-alloys consisting of a lamellar structure, comprising gamma-phase plus a small amount of alpha2-phase, with addition of 1, 5 and 10at% Nb were prepared. The samples were investigated by means of field ion microscopy (FIM) and atom probe tomography (APT). The influence of doping elements on the variation of field evaporation and microstructural parameters in the gamma-phase as studied by FIM and APT will be reported in this contribution. The intermetallic gamma-Phase of TiAl exhibits a L1(0)-structure, which has alternating Ti- and Al-planes in the [001]-superstructure direction. Because of the significant difference in the evaporation field strengths of Ti and Al, it is usually not possible to directly distinguish Ti- and Al-planes in this direction in the APT data. Therefore, it is not possible to assign Nb to any plane, as well. To solve this problem an algorithm, using statistical methods, was developed, which allows to inherently distinguish the planes. A comparison of the results for [100]- and [001]-directions shows that Nb prefers Ti-sites. The sequence of field evaporation field strengths, which follows the trend E(Nb) > E(Al) > E(Ti), could also be deduced.
制备了由层状结构组成的双相TiAl/Ti3Al合金，其包含γ相和少量α2相，并添加了1at%、5at%和10at%的Nb。通过场离子显微镜（FIM）和原子探针断层扫描（APT）对样品进行了研究。本论文将报道通过FIM和APT研究掺杂元素对γ相中场蒸发和微观结构参数变化的影响。TiAl的金属间γ相具有L1(0)结构，在[001]超结构方向上具有交替的Ti和Al平面。由于Ti和Al蒸发场强存在显著差异，在APT数据中通常无法直接区分该方向上的Ti和Al平面。因此，也无法将Nb分配到任何平面上。为了解决这个问题，开发了一种使用统计方法的算法，该算法能够内在地区分这些平面。对[100]和[001]方向结果的比较表明，Nb更倾向于占据Ti位点。还可以推断出场蒸发场强的顺序为E(Nb) > E(Al) > E(Ti)。
