The evolution of microstructure and toughness in multipass welds that contain acicular ferrite.

本项目涉及多道次钢焊缝韧性的基础研究。焊接韧性对于建筑行业、风能行业、火力发电和石化行业等众多行业的结构和部件至关重要。“韧性”一词是指材料在断裂前吸收能量的能力。韧性在抵抗裂纹扩展和避免突然失效方面尤为重要。在诸如核工业中出现的安全关键应用中，反应堆压力容器或蒸汽发生器等部件的安全运行在很大程度上取决于焊接接头的韧性。该职位的成功候选人将参与焊接试件的制造，焊接机械测试的协调，以及通过电子显微镜进行详细的微观组织表征。在考虑工业应用的基础上，将选择至少两种不同的焊缝填充材料进行研究。作为研究的一部分，还可以对化学成分（即C， Mn, Cr, Mo, Ni, Cu, Ti， O的浓度）已经仔细和系统地变化的钢试件进行一些微观结构分析，以便获得可能导致设计新的填充材料的见解和理解。显微镜和整个研究项目的重点将是深入了解以下几点：-在单道次焊接过程中控制针状铁素体形成的因素，因为针状铁素体的存在与优异的焊接韧性有关；-针状铁氧体在后续热循环中再加热时形成的相；-针状铁素体转变为其他微相后（由于在多道焊缝中随后的热循环）影响其表观韧性的因素。热输入和焊接条件对焊缝金属微观结构的影响这项工作将涉及光学和扫描电子显微镜（OM/SEM），以及电子探针微观分析（EPMA），以及能量和波长色散光谱（EDS/WDS）。成功的候选人有望成为钢的焊接冶金专家和电子显微镜专家。在这个项目中发展的技能组合将为博士课程结束后的许多不同职业选择提供理想的平台。

This project involves a fundamental study on the toughness of multipass steel welds. Weld toughness is of vital importance to structures and components across a wide range of industries, including the construction sector, the wind energy sector, thermal power generation, and in petrochemical industries. The term "toughness" refers to the ability of a material to absorb energy prior to fracture. Toughness is particularly important in resisting the propagation of cracks and avoiding sudden failures. In safety-critical applications such as those that arise in the nuclear industry, the safe operation of components such as the reactor pressure vessel or a steam generator strongly depends on the toughness of welded joints. The successful candidate for this post will be involved in the manufacture of weld test pieces, the coordination of mechanical testing on the welds, and detailed microstructural characterisation through electron microscopy. At least two different weld filler materials will be chosen for investigation on the basis that they are under consideration for industrial application. As part of the research, some microstructural analysis may also be carried out on steel test pieces for which the chemical composition (i.e. the concentrations of C, Mn, Cr, Mo, Ni, Cu, Ti, O) has been carefully and systematically varied, in order to gain insights and understanding that could lead to the design of a new filler material. The focus of the microscopy and the overall research project will be to develop a deep understanding of the following:- The factors that control the formation of acicular ferrite during a single weld pass, since the presence of acicular ferrite is associated with excellent weld toughness;- The phases that form when acicular ferrite is reheated by subsequent thermal cycles;- The factors that influence the apparent toughness of acicular ferrite after it has transformed into other microphases (due to subsequent thermal cycles in a multipass weld).- The influence of heat input and welding conditions on the weld metal microstructureThe work will involve both optical and scanning electron microscopy (OM/SEM), as well electron probe micro-analysis (EPMA), and both energy- and wavelength-dispersive spectroscopy (EDS/WDS). The successful candidate can expect to emerge as an expert in the welding metallurgy of steels, and as an expert electron microscopist. The combination of skills that will be developed in this project will provide an ideal platform for a number of different career options after the PhD programme.