氢对铝位错行为及开裂机理影响的原位定量研究

Hydrogen embrittlement (HE) is a phenomenon, in which materials lose ductility due to hydrogen absorption and hence are prone to fracture at lower stress level. Even now, catastrophes still happen in infrastructure, petrochemical, nuclear, hydrogen energy and ocean industries, resulting in huge loss of life and property. After investigation of over a century, the HE mechanism remains murky. Many research work agree that HE phenomena in various materials may have similar origin in microscale mechanism. However, HE related microscale experimental exploration is too challenging to make a breakthrough. In this project, we adopt the advanced in situ environmental TEM technique and in situ quantitative nanomechanical tests including compression, tension, bending, cracking, to investigate the modal material of aluminum. The investigation will systematically tackle the fundamental hydrogen effects on the evolution of typical lattice defects, such as dislocations and grain boundaries, as well as the cracking process in aluminum. These investigations may help resolving the above-mentioned debates by providing key experimental facts as evidence. Based on the experimental results, we aim to map out the hydrogen-defect interaction, revise or refresh the established HE mechanism.

氢脆是指当材料内部因含氢而塑性降低，甚至由此引发低应力断裂失效的现象。在基础设施、石化、核、氢能、海洋等工业中，由氢脆引起的安全事故仍然时有发生并因此造成巨大经济损失。尽管氢脆研究已逾百年，但其机理仍不清楚。许多研究认为各种材料的氢脆现象很可能在微观机理上存在一些相同起源，然而相关的微观尺度研究探索难以取得突破性进展。本项目拟采用最新的原位环境透射电子显微技术，以铝为模型材料进行压缩、拉伸、弯曲、开裂等定量的纳米力学实验，系统地研究变形过程中氢对位错、晶界等晶格缺陷行为，以及对开裂过程的影响。这些研究结果将为氢脆机理争论点的解决提供关键的实验证据，揭示氢和典型材料缺陷交互作用规律，修正现有的氢脆理论。

金属工程材料的氢脆现象是其在汽车、石化、航空航天等领域的安全服役的重要威胁。氢脆现象起源在于氢与材料缺陷有较强的交互作用，使得材料的变形行为发生改变，塑性降低，容易发生延滞断裂。本研究将原位环境透射电镜技术和纳米力学测试技术结合应用，深入研究了氢与金属铝中的一些常见缺陷的交互作用，主要创新性发现如下：.1）.系统研究了氢对金属铝中的位错行为及力学特性的影响。发现在金属铝中，充氢能降低杨氏模量达3%，增加位错滑移阻力，促进位错环通过攀移发生的湮灭。以上发现共同证明了充氢后金属中含有的过饱和浓度的空位是到这这些变化的主要原因。.2）.研究了充氢对金属铝的裂纹形核及扩展行为的影响。发现裂纹在扩展过程中会在裂尖动态生成小角晶界，此种小角晶界在含氢情况下具有更高的开裂倾向。该发现直观地揭示了一种氢致穿晶开裂新机理：氢通过弱化裂尖小角晶界促进开裂。