γ-Ni_γ-Ni3Al相界区域N的占位与脆化作用分析.docVIP

 γ-Ni/γ-Ni3Al 相界区域 N 的占位与脆化作 用分析# 彭黎，贺双，彭平** 5 10 15 20 25 30 35 40 （湖南大学 材料科学与工程学院，长沙 410082） 摘要：采用第一原理赝势平面波方法调查了迹量元素 N 在 γ-Ni/γ′-Ni3Al 相界区域的占位趋 势及其对相界断裂强度的影响。结果显示：以气态形式存在的 N 不易掺杂到 Ni/Ni3Al 相界， 而以固态形式存在的 N 则很容易被掺进 Ni/Ni3Al 相界；N 在 Ni/Ni3Al 相界中不仅能稳定存 在，而且掺杂到八面体间隙比置换其中的基体原子具有更高的形成能力与结构稳定性。N 掺 杂将削弱 Ni/Ni3Al 相界的断裂强度，其中尤以间隙位掺杂最为明显。电子结构分析表明： 置换型掺杂时，相界断裂强度的降低可归结为 Frenkel 缺陷导致的掺杂相界层间电子相互作 用的减弱；而间隙位掺杂，除了基体原子间电子相互作用因掺杂原子与基体原子间的强相互 作用而减弱外，晶格畸变导致的局域弹性应变能增加也是一个重要的原因。 关键词：γ-Ni/γ′-Ni3Al 相界；N 掺杂；第一原理计算；脆化；电子结构 中图分类号：TG132.33 Site preference of N and N-induced embrittlement at the γ-Ni/γ-Ni3Al interface PENG Li, HE Shuang, PENG Ping (School of Materials Science Engineering, Hunan University, Changsha 410082, China) Abstract: Using a first-principles plane-wave pseudopotential method, the site preference of N and its influence on the fracture behavior of the γ-Ni/γ-Ni3Al interface have been investigated. Results show gaseous N2 is difficult to be joined into the Ni/Ni3Al interfacial region, but solid N impurity can be easily doped into the Ni/Ni3Al interface. The N-doped interfacial system can stably exist either for substitution for host atoms or for occupation at octahedral interstices, and N prefers to occupy the octahedral interstitial sites. N-doping, especially at octahedral interstitial sites, makes the fracture strength of the Ni/Ni3Al interface be weakened. For the substitutional interface, the N-induced embrittlement can be attributed to a decrease of electronic interactions between adjacent atomic layers caused by the Frenkel defect. While in the case of interstitial doping, a multiple influence of a decreasing electronic interaction between host atoms induced by a strong bonding between N and its nearest host atoms and a increased elastic strain energy originated from lattice distortion should be responsible for the harmful effect of N on the strengthening of the Ni/Ni3Al interface. Key words: -Ni/γ-Ni3Al interface; N-doping; first-principle calculation; embrittlem