塑性变形过程溶质偏聚对晶界演化影响的晶体相场研究

Solute segregation at grain boundary can significantly influence the mechanical properties of polycrystal metal materials. In the presence of solute segregation at grain boundary, the dynamic interaction behavior between dislocation and grain boundary and their evolution during plastic deformation become complicated. Understanding the effects of solute segregation on microscopic deformation mechanism of metal materials, is the key to control and design the mechanical properties through “grain boundary engineering” and “grain boundary segregation engineering” methods.. In this proposal, an advanced multiscale simulation method, the X phase-field crystal model is used to study the effects of solute segregation on grain boundary evolution during low strain rate deformation of binary Nickle based alloy. The contents of this project include the followings: studying the static and dynamic interaction between grain boundary, dislocation and solute atoms, exploring the atomic mechanism of solute segregation and the effects of atomic structure of grain boundary on the solute segregation, and the influences of solute segregation on grain boundary evolution during plastic deformation. Furthermore, the relationship between atomic structure of grain boundary, grain boundary solute segregation and grain boundary evolution during plastic deformation is studied, and the reverse design principles for improving and controlling the materials properties will be proposed, and then, verified by the experimental study and testing. By the study of this project, it is expected to reveal the atomistic mechanism of solute segregation effect on plastic deformation process, and provide a theoretical guideline for improving and controlling the mechanical properties by designing the composition and microstructure of alloys.

溶质偏聚影响金属材料的力学性能。塑性变形过程晶界和位错的交互作用及演化，在晶界溶质偏聚的条件下，动力学过程变得复杂。理解和认识溶质偏聚对金属塑性变形微观过程影响的规律和机制，是通过“晶界工程”和“晶界偏聚工程”方法改善材料力学性能的核心与关键。.本项目以二元镍基合金为主要对象，采用结构晶体相场模型这一先进多尺度模拟方法，通过模拟低应变速率塑性变形过程的微结构演化，研究晶界、位错和溶质之间的静态和动态交互作用，探索晶界原子尺度结构对溶质偏聚的影响规律和机理，阐明溶质偏聚对塑性变形过程中晶界演化动力学过程影响的规律和机制，建立晶界原子尺度结构、晶界成分偏聚与塑性变形过程晶界演化动力学过程之间的内在关联，提出逆向设计原则，并进行实验分析和验证。通过本项目的研究，揭示溶质偏聚对塑性变形过程影响的原子尺度机制，可为金属成分和微结构的设计、力学性能的控制，提供理论支撑，有学术研究价值。

溶质偏聚影响金属材料的力学性能。塑性变形过程晶界和位错的交互作用及演化，在晶界溶质偏聚的条件下，动力学过程变得复杂。国外为研究溶质偏聚对金属塑性变形微观过程影响的规律和机制，进而改善材料力学性能，在“晶界工程”的基础上提出了“晶界偏聚工程”的概念。“晶界偏聚工程”概念的提出，对认识和理解晶界偏聚诱导的热力学特性和动力学过程提出了新的挑战，即如何在原子尺度实现对晶界结构和化学成分的表征，进而在原子尺度研究晶界偏聚对界面热力学和动力学规律的影响。晶体相场被视为在原子尺度上研究晶界化学成分和力学性能之间影响规律的可靠手段之一。.本项目采用晶体相场模型，通过模拟纯物质和二元合金的凝固过程及变形过程，研究了纳米多晶、纳米孪晶和双晶的原子尺度变形过程，探明了不同晶界结构在塑性变形过程中晶界与位错的动态交互作用、以及溶质偏聚对晶界演化的影响规律。研究结果表明不同晶界处的溶质原子偏聚程度不同，晶界处的共格程度越高，溶质偏聚程度越小；晶界不仅可以发射位错还可以吸收位错，晶界处的共格程度越高，晶界发射位错的阈值越高，溶质偏聚提高位错发射的阈值；溶质偏聚对晶界演化规律的影响机制来源于溶质原子的拖拽效应和钉扎效应。