氢致金属变形失效的多场/多尺度研究与定量表征

Hydrogen-induced metal failure is a key challenge in the future development and utilization of hydrogen energy. Hydrogen can weaken metallic bond and aggravate vacancy nucleation and conglomeration, causing a reduction of the cohesion strength of metal. Hydrogen can also accelerate dislocation nucleation, movement and multiplication, leading to an increase in plastic deformation. As a result of the combined effects of these two factors, hydrogen-induced metal failure appears brittle at macro-scale but ductile at micro/meso-scale, which is typically characterized as a "multi-physical field/multi-defect/multi-scale coupled dynamics (3MCD)" problem. It involves not only hydrogen diffusion, entrapment and transport, but also interactions of multiple material defects induced by the hydrogen, such as the vacancy-point defect, dislocation-line defect, grain/phase boundary-face defect, and void/crack-volume defect. In this project, the quantitative relation between the hydrogen-induced brittleness at macro-scale and ductility at micro/meso-scale will be investigated in details, with a special emphasis on the hydrogen-induced interaction between multi-defects. First, a series of micro-/meso-/macro-scopic tests will be performed, aiming to uncover the 3MCD mechanisms of hydrogen-induced metal failure by using the high-resolution TEM/SEM. Next, a meso-scopic hydrogen diffusion and multi-defect coupled dynamics program, together with a continuum hydrogen diffusion and crystal plasticity coupled dynamics program, will be developed, based on the proposed theories and computational schemes. Then, multiple coupled simulations will be carried out to compare with the corresponding experimental results, so as to quantitatively relate the brittle failure behaviors at macro-scale to the plastic deformation and damage mechanisms at micro-/meso-scale. Finally, a new hydrogen-induced enhanced plasticity-mediated vacancy damage and decohesion mechanism will be developed and a hydrogen-induced failure criterion will be presented. These studies can provide strong theoretical and technological supports to safety defence、design and assessment of materials and structures operating in hydrogen environment.

氢致材料失效是未来氢能源开发、利用中面临的重要难题。氢会削弱金属键并促进空位演化，导致金属粘聚强度降低；同时，会促进位错形核、运动和增殖，导致塑性增强。在两者共同作用下，氢致金属失效宏观上表现为脆性但微细观上为韧性。它是典型的多场/多维缺陷/多尺度耦合动力学（3MCD）问题，涉及氢扩散、捕捉和输运，以及氢致多维缺陷之间复杂的相互作用，人们对其物理机制和过程不甚明了。本项目拟围绕氢致多维缺陷相互作用机理这一关键科学问题，通过微细宏观实验，直观揭示氢致失效的3MCD机理；发展氢扩散-多维度缺陷耦合动力学和氢扩散-晶体塑性耦合动力学理论、算法和程序，实现对氢致失效的3MCD模拟；结合系列实验和复杂过程多尺度模拟对比分析，从3MCD的新角度，定量表征氢致宏观脆性和微细观韧性间的跨尺度关联；提出氢增强塑性协调的损伤失效机制和氢致失效准则。为氢环境下材料和结构的安全防护、设计和评定提供理论和技术支持。

氢致材料力学性能退化长期困扰着化工、核电、船舶海洋工程等众多的传统工业部门，是一个亟待解决的重要科学和技术问题。氢致材料力学性能退化现象背后隐藏着极其复杂的“氢-金属键-多维缺陷”相互作用机理，属于典型的多物理场/多维缺陷/多尺度耦合力学问题，发展氢致塑性变形模型、损伤理论及失效判据是固体力学研究的前沿课题，具有重要的学术价值和深远的科学意义，富有挑战性。..本项目围绕氢致多维缺陷相互作用机理及其定量表征这一核心科学问题，通过宏-细-微观实验测试、理论建模和计算模拟，首先，建立了一系列包含原子尺度信息的“氢-位错-缺陷”相互作用法则；提出了氢与位错相互作用的连续统理论及模拟方法，发展了包含原子尺度信息的相场动力学（PFD）及多维度缺陷耦合动力学（MDCD）算法，提出了基于细观力学的多维度缺陷相互作用弹性理论，系统研究了氢与多维度缺陷的相互作用，深刻揭示了氢致断裂及其韧脆转变的微细观机制；其次，提出了“机理型”和“唯象型”晶体塑性本构，建立了氢扩散、氢输运及塑性变形耦合理论，模拟研究了充氢多晶材料的单调及循环塑性行为；再次，通过微纳米压痕及拉、压、扭、弯单调及循环实验，揭示了氢对金属塑性变形、断裂损伤及疲劳破坏的影响，发展了考虑氢效应的Gurson损伤模型，提出了以细观尺度非均匀应变分布参量度量材料疲劳寿命损失并描述氢致疲劳规律的方法，再现了典型金属的氢致断裂模式转变及氢致疲劳寿命缩短等重要实验现象。本项目的研究成果，为氢致塑性变形及断裂损伤研究提供了多场/多尺度力学理论、计算模拟方法和实验测试方法。..该项目顺利完成各项预定目标。目前已发表期刊论文41篇。培养博士后3人，毕业博士生12人，在读博士生8人，毕业硕士生8人。项目成员参加国内外学术会议80余次，组织国内学术会议3次，邀请海外学者来访并开展学术交流8人次。依托该项目，项目负责人在华中科技大学组建了极端环境力学研究团队。