Modelling environmentally assisted cracking in Ni-based superalloys

镍基高温合金由于其高强度和抗蠕变性而广泛用于航空发动机应用中，例如燃气涡轮盘或叶片。然而，氧在高温下扩散到材料中可能导致称为环境辅助开裂（EAC）的复杂失效过程。由于燃料效率要求和减少排放的需要，飞机发动机制造商被迫将工作温度提高到700 oC以上，这些合金中的EAC变得越来越普遍，现在是其在航空发动机应用中使用的主要限制。EAC涉及许多相互竞争的机械和化学过程，更好地了解这些过程对于预测当前使用的合金的寿命以及开发新的耐EAC材料至关重要。该博士项目的目的是研究成分和微观结构的变化如何影响镍基高温合金对EAC的敏感性。EAC敏感性受到元素氧的吸收速率、材料对生长氧化物的亲和力以及适应材料中积累的应力的弛豫机制的强烈影响。学生将为这些高度相关的过程开发计算模型，并将这些模型应用于研究新开发合金的EAC行为，以及它们与目前使用的标准合金和微观结构的比较。该职位的候选人应具有材料科学，物理或相关学科的学位，并具有较强的计算能力。经验是材料建模是有帮助的，但不是必不可少的，但是候选人应该热衷于使用数学和计算机来模拟材料的行为。这个博士职位将由劳斯莱斯赞助。将有机会花时间在劳斯莱斯，并有助于由其他大学合作伙伴领导的中子和同步加速器衍射实验。除了培养优秀的计算建模技能外，博士生还将获得先进镍基高温合金及其在航空发动机中的应用方面的专业知识。

Ni-based superalloys are extensively used in aero-engine applications, such as gas-turbine discs or blades, due to their high strength and creep resistance. However, oxygen diffusion into the material at elevated temperatures can lead to in a complex failure process known as environmentally-assisted cracking (EAC). With aircraft engine manufacturers driven to increase operating temperatures in excess of 700 oC due to fuel efficiency demands and the need to reduce emissions, EAC in these alloys is becoming increasingly prevalent and is now the major limitation to their use in aero-engine applications. EAC involves many competing mechanical and chemical processes, and a better understanding of these processes is essential to predicting the life of currently used alloys as well as the development of new EAC-resistant materials.The aim of this PhD project will be to investigate how changes in composition and microstructure affect the susceptibility of Ni-based superalloys to EAC. EAC susceptibility is strongly influenced by the rate of uptake of elemental oxygen, the affinity of the material to grow oxides and relaxation mechanisms to accommodate stresses that build up in the material. The student will develop computational models for these highly interrelated processes, and will apply these models to investigate EAC behaviour in newly developed alloys and how they compare with more standard alloys and microstructures currently used.Candidates for this position should have a degree in Materials Science, Physics or related discipline with strong computational skills. Experience is materials modelling is helpful but not essential, however candidates are should be enthusiastic about using mathematics and computers to model materials behaviour. This PhD position will be sponsored by Rolls-Royce. There will be opportunities to spend time at Rolls-Royce and contribute to neutron and synchrotron diffraction experiments led by other university partners. As well as developing excellent computational modelling skills, the PhD student will acquire expertise in advanced Ni-based superalloys and how they are used in aero-engines.