长期以来，材料性能的提升往往依赖于合金化思路，但随着需求量日增，对材料性能的要求日渐苛刻，导致合金材料成本不断攀升，而合金性能的提升随着合金化元素的增多也逐渐趋缓。同时，废弃合金对材料的回收利用也带来挑战。合金化的本质是引入其它元素，改变原有晶体的电子态、应变场或形成新相，以期提升材料性能。由于孪晶、堆垛层错和晶界等面结构在晶体中广泛存在，且同样具有改变晶体原有电子态和应变场的作用。因此可以通过减少或不使用合金元素，通过对晶体中的内禀界面进行纳米结构化设计来实现材料性能的提升。从而替代合金化，减少合金元素的使用，促进材料的回收和再利用。本文研究对象镍基超合金中基体Ni与增强相Ni₃Al呈镶嵌式共格结构，且增强相Ni₃Al的超晶格结构使其具有特殊的面结构，如超晶格内禀堆垛层错、复杂堆垛层错、反相畴界和孪晶界。同时超合金中的Ni/Ni₃Al共格界面对其力学性能的影响亦不可忽视，这使得存在至少五种界面来调控和改善其力学性能。因此采用纳米结构化设计策略来提升镍基超合金的力学性能不失为一条有开拓性的蹊径。本文主要从面结构调控机制和Ni/Ni₃Al异质共格界面调控机制两个方面开展研究。

在面结构调控机制方面，通过研究增强相Ni₃Al中已知的超晶格内禀堆垛层错、复杂堆垛层错、反相畴界和孪晶界四类典型的面结构与位错的相互作用，阐明了面结构的强韧化规律和微观力学机制，揭示了位错与面结构的相互作用机理，主要的研究结论如下：

（1）超晶格内禀堆垛层错和孪晶界的强韧化机理：超晶格内禀堆垛层错可显著地提高Ni₃Al纳米线的强度和韧性，相较于孪晶，超晶格内禀堆垛层错的强韧效果更为明显，且两者强度分别与其特征尺寸的1次方和1/2次方成反比。两种面结构的强化因子是超晶格内禀堆垛层错与孪晶界对位错的阻碍作用以及钉扎效应，软化因子是孪晶迁移和退孪晶。强化和软化因子的竞争机制导致超晶格内禀堆垛层错和孪晶界具有择优强韧化机制。

（2）复杂堆垛层错和孪晶界的硬化机理：复杂堆垛层错和孪晶界都可实现硬化效果，并且同时具有特征尺寸择优硬化机制，两者特征尺寸临界值为3 nm。在临界值以下，复杂堆垛层错的硬化效果强于孪晶界，反之亦然。复杂堆垛层错和孪晶界的硬化因子主要是面结构对位错运动的阻挡、超晶格内禀堆垛层错的形成以及位错钉扎效应。软化因子主要为复杂堆垛层错的褪去、退孪晶和孪晶迁移。

（3）纳米压入中主导Pop-in事件的位错反应机理：通过浅压痕纳米压入实验和分子模拟，揭示了超合金压入过程中的Pop-in事件是由位错反应引起堆垛层错四面体的形成所导致的，Pop-in事件的连续发生对应着Ni₃Al中堆垛层错四面体的连续构建。此外，建立了位错中储存的应变能与外力功之间能量转换的理论模型，两者之间的动态平衡导致压入过程中Pop-in事件的连续产生。

（4）面结构与棱柱型位错环对交互作用机理：首次在Ni₃Al发现了棱柱型位错环对结构，并探究了超晶格内禀堆垛层错、复杂堆垛层错、孪晶界和反相畴界与位错环对的交互作用机制，研究表明面结构能有效地阻碍位错环的运动，即面结构能有效提升材料力学性能。并建立了位错/结构碰撞界面增强模型，提出了界面阻挡系数的概念，定量地表征了四类面结构的硬化效果。

在Ni/Ni₃Al异质共格界面调控机制方面，采用分子模拟揭示了镍基超合金增强相与基体之间的共格界面失配位错网络结构，探究了共格界面失配位错网络在镍基超合金中的调控机理。主要的研究结论如下：

（1）异质共格界面失配位错网络与刃位错偶极子对交互作用机理：首次在镍基超合金中构建了刃位错偶极子对，并探究了共格界面失配位错网络与刃位错偶极子对的交互作用机制。研究表明界面失配位错网络可有效阻碍和吸收基体位错，使其在界面处堆积实现强韧效果。并建立了刃位错偶极子激发周期加载率效应的理论模型，得到了计算特定位错形成能的新手段。

（2）镍基超合金屈服强度温度奇异性的分子机制：镍基超合金因其特殊的异质共格界面失配位错网络结构，在高温环境下呈现独特的屈服奇异性。首次通过分子模拟揭示了镍基超合金中三维共格界面失配位错网络结构演化的温度效应，阐释了其屈服强度奇异性行为的位错演化机制，表明镍基超合金屈服奇异性是由于不同位错的发展及滑移系激发顺序所主导，为实验上镍基超合金的屈服奇异性给出了原子尺度的合理解释。

Over the past several decades, the improvement of material properties often depends on the alloying strategy. However, with the increasing demand, the requirements for material properties become harsher, leading to the alloy materials becoming costlier, and the improvement of alloys properties gradually slows down with the augment of alloying elements. Meanwhile, the abandoned alloys also bring challenges to the recycling of materials. The nature of alloying strategy is to introduce other elements to change the electronic states, strain fields or form new phases of the original crystal to improve the material properties. In addition, the twinning boundary, stacking faults and grain boundary widely exist in the crystalline materials, and they can also change the original electronic states and strain fields. Therefore, nanostructured design of intrinsic interfaces can be achieved by reducing or eliminating alloying elements to improve material properties. This strategy can replace alloying and promote material recovery and reuse. In this work, the matrix phase Ni and the precipitate phase Ni₃Al of Ni-based superalloy are mosaic coherent structures, and the superlattice structure of the precipitate phase Ni₃Al makes it have special planar structures, such as superlattice intrinsic stacking faults, complex stacking faults, antiphase boundary and twin boundary. At the same time, the effects of Ni/Ni₃Al heterogeneous coherent interface on the mechanical properties of superalloy cannot be ignored, so there are at least five intrinsic interfaces to regulate and improve the mechanical properties of Ni-based superalloy. Therefore, adopting nanostructured design methods to improve the mechanical properties can be regarded as a pioneering strategy. This project mainly focuses on the planar structure regulation mechanisms and Ni/Ni₃Al heterogeneous coherent interface regulation mechanisms.

In terms of planar structure regulation mechanisms, the interaction between four types of typical planar structures (superlattice intrinsic stacking faults, complex stacking faults, antiphase boundary, twin boundary) and dislocations have been explored, and the strengthening and toughening of planar structures and microcosmic mechanical mechanisms have been revealed. The main conclusions are as follows:

(1) Strengthening and toughening mechanisms of superlattice intrinsic stacking faults and twinning boundary: Superlattice intrinsic stacking faults can significantly improve the strength and toughness of Ni₃Al nanowires compared with twinning boundary. Strengthening by superlattice intrinsic stacking faults and twinning boundary can be described by the Hall-Petch relationship with an exponent of 1 and 1/2, respectively. The strengthening and toughening favorable factors are attributed to the impediment of two planar structures to the propagation of dislocations and pinning effect resulting from the interaction between dislocations and planar structures. Disadvantageous aspects include fading of detwinning and migration of twinning boundary. The competitive mechanism of strengthening and softening factors leads to the preferential strengthening and toughening of superlattice intrinsic stacking faults and twinning boundary.

(2) Hardening mechanism of complex stacking faults and twinning boundary: Hardening can be achieved by planar structures such as complex stacking faults and twinning boundary with single crystal Ni₃Al as a reference. There is the same hardness of complex stacking faults and twinning boundary at a critical spacing of 3.0 nm between parallel planar structures. Below the spacing value, the hardening effect of complex stacking faults is stronger than twinning boundary. Hardening factors are attributed to impediment of planar structures to propagation of dislocations, generation of superlattice intrinsic stacking faults and pinning effect resulting from the interaction between dislocations and planar structures. Softening aspects include fading of complex stacking faults, detwinning and migration of twinning boundary.

(3) Dislocation reactions dominated pop-in events in nanoindentation: From experimental and atomistic simulation perspectives, the dislocation reactions dominated pop-in events in Ni-based superalloys under nanoindentation have been elaborated. It is shown that, due to dislocation reactions, the pop-in events correspond to construction of stacking faults tetrahedrons. The magnitudes of displacement bursts are proportional to the number and size of stacking faults tetrahedrons. A theoretical model is built to analyze the energy conversion between the external work and strain energy stored in dislocations. The balance of energy conversion between external work and strain energy yields a plateau in a force-depth curve, denoting occurrence of a pop-in event.

(4) Interactions mechanisms between prismatic dislocation loop pairs and planar structures: Prismatic dislocation loops are always generated in pairs with a butterfly-like shape and hardening can be achieved by planar structures such as the twinning boundary, superlattice intrinsic stacking fault, complex stacking fault and antiphase boundary with a single crystal as a reference. The planar structures can effectively block the movement of the prismatic dislocation loop pairs and play a hardening role. The hardening effects and interaction mechanisms between the prismatic dislocation loop pairs and planar structures have also been systematically elucidated. Furthermore, the interface enhancement model of dislocation/structure collision was established, and the concept of interface impeding coefficient was proposed to quantitatively characterize the hardening effect of four types of planar structures.

In terms of the regulation mechanisms of Ni/Ni₃Al heterogeneous coherent interface, the molecular dynamic simulation was used to reveal the structures of the interfacial misfit dislocation network, the dominated mechanisms of the Ni/Ni₃Al interfacial misfit dislocation network have been explored. The main conclusions are as follows:

(1) Interaction mechanisms between the edge dislocation dipole pair and interfacial misfit dislocation network: Perfect edge dislocation dipole pairs have firstly been constructed in Ni matrix, and then, interaction mechanisms have been investigated between edge dislocation dipole pairs and interfacial misfit dislocation network. It is shown that, the interfacial misfit dislocation network can impede, accommodate and pile up edge dislocation dipole pairs in Ni matrix, and make them accumulate at the interface to achieve strengthening and toughening effect. Furthermore, the influences of loading rates on the stimulating period of edge dislocation dipole pairs have been systematically elucidated, and the theoretical model of loading rate has been constructed, which also obtain a new method to calculate the specific dislocation formation energy.

(2) Molecular mechanism of yield strength anomaly of Ni-based superalloy: Ni-based superalloy presents unique yield strength anomaly at high temperature due to its special heterogeneous coherent interfacial misfit dislocation network structures. From an atomistic perspective, the temperature effects of the structural evolutions of the three-dimensional interfacial misfit dislocation network have firstly been explored. The anomalous behavior of yield strength is dominated by the development of different dislocations and the activation sequence of the slip systems, which provides the atomic scale explanation for the yield strength anomaly of Ni-based superalloy.