【作者】 刘丽丽；

【导师】 黄仁忠；

【作者基本信息】 沈阳师范大学 ， 凝聚态物理， 2022， 硕士

【摘要】 γ′-Ni₃Al作为镍基高温合金的关键强化成分,被广泛用于商用合金中。但因其低的高温蠕变强度和本征脆性而严重影响了其应用。研究表明添加Mn元素可以提高Ni₃Al的延展性。但对于Mn在Ni₃Al中的占据行为,由于实验条件的不同导致Mn的占据有所不同。Mn在Ni₃Al中的占位倾向仍需进一步研究。由于添加B可以进一步增强Mn改善合金延展性的成分范围,且B易向Ni/Ni₃Al界面偏聚,对界面处Mn占位的影响也不能忽视。因此在本研究中同时考虑两者的协同作用对Ni₃Al合金及Ni/Ni₃Al界面性能的影响。本文运用第一性原理方法首先研究Mn在B掺杂前后的Ni₃Al中占位行为与成分及温度之间的关系,分析B、Mn共合金化对Ni₃Al合金力学性能的影响。然后探究Ni/Ni₃Al界面以及B掺杂的Ni/Ni₃Al界面中Mn的占位情况,分析B、Mn对Ni/Ni₃Al界面稳定性的影响。研究得到的结论如下:（1）在研究的整个温度范围内,B始终占据八面体间隙位置,而不是四面体间隙位置。与由Ni、Al原子组成的八面体间隙位置相比,B更倾向于占据全部由Ni原子组成的八面体间隙位置。（2）Mn在Ni₃Al中的占位受温度及成分的影响。在Ni₃Al合金中,温度为0K时,锰随机占据镍位或铝位。随着温度升高,在富铝的合金中,锰的占据偏好镍位变为偏好铝位;在正常化学计量比合金中,锰由随机占据镍位或铝位变为占据铝位;富镍合金中,锰始终占据铝位。B的添加抑制了Mn占位倾向的转变。（3）通过对不同结构力学性能的分析发现,所有Mn取代的Ni₃Al结构的延展性均得到不同程度的改善。特别的,B和Mn无论是单独合金化还是同时合金化都使得Ni₃Al的延展性增强。（4）Mn的取代使Ni/Ni₃Al界面的稳定性增强。晶格发生错配时,Ni/Ni₃Al体系的稳定性均会降低。在Ni₃Al相区,错配度范围内Mn均占据铝位;在界面区Ni₃Al中,随着错配度逐渐增加,Mn的占据倾向由随机占据Ni、Al位变为弱占据Al位。（5）掺杂B后Ni/Ni₃Al界面体系稳定性进一步增强。在错配度为4.4%掺杂B的情况下,锰原子在Ni/Ni₃Al界面区的占据从占据铝位转变为占据镍位,但占据倾向较弱。更多还原

【Abstract】 γ′-Ni₃Al is widely used in commercial alloys as a key strengthening component of nickel-based superalloys.However,its application is seriously affected by its low high temperature creep strength and intrinsic brittleness.Some studies have shown that adding Mn can improve the ductility of Ni₃Al.But for the occupation behavior of Mn in Ni₃Al,experimental results are different due to different experimental conditions and further research is needed.Because of B segregation at the Ni/Ni₃Al interface,the addition of B and Mn further enhances the composition range of the ductility of the alloy and the effect of B on the Mn occupation at the interface cannot be ignored.Therefore,the synergistic effect of B and Mn on the properties of Ni₃Al alloy and Ni/Ni₃Al interface has been considered in this study.In this paper,the first-principles method was used to study the relationship of the occupancy behavior of Mn in Ni₃Al before and after B doping with composition and temperature to further explore the effect of B and Mn co-alloying on the mechanical properties of Ni₃Al alloy.Then,the occupancy of Mn in the Ni/Ni₃Al interface and the B-doped Ni/Ni₃Al interface was investigated,and the effect of B and Mn on the stability of the Ni/Ni₃Al interface was analyzed.The conclusions are as follows:（1）Over the entire temperature range studied,B consistently occupies octahedral,but not tetrahedral,interstitial sites.Compared with the octahedral interstitial sites composed of Ni and Al atoms,B tends to occupy the octahedral interstitial sites composed entirely of Ni atoms.（2）The occupancy of Mn in Ni₃Al is affected by temperature and composition.In Ni₃Al alloys,Mn randomly occupies Ni sites or Al sites at 0 K.With the increase of temperature,in Al-rich alloys,the occupation of Mn prefers Ni sites to prefer Al sites;in normal stoichiometric alloys,it changes from randomly occupying Ni sites or Al sites to occupying Al sites;Ni-rich alloys,Mn always occupies the Al site.The addition of B suppressed the transition of Mn occupancy tendency.（3）Through the analysis of different structural mechanical properties,it is found that the ductility of all Mn-substituted Ni₃Al structures has been improved to varying degrees.In particular,both B and Mn,whether alloyed alone or simultaneously,enhance the ductility of Ni₃Al.（4）The addition of manganese enhances the stability of the Ni/Ni₃Al interface while the stability of the Ni/Ni₃Al system will decrease due to the lattice mismatch.In the Ni₃Al phase region,manganese occupies the aluminum sites in the range of lattice misfit.With the increase of lattice misfit,the occupation tendency of manganese changes from randomly occupying the nickel or aluminum sites to the aluminum sites with a weak tendency in the interface region Ni₃Al.（5）The stability of the Ni/Ni₃Al interface is further enhanced by boron doping.When the lattice mismatch is 4.4%,the occupation behavior of Mn in Ni/Ni₃Al interface region changes from occupying the Al sublattice to the Ni sublattice,however the occupation tendency is still weak.更多还原