Yiqiang Wang

Structural integrity for fusion is an integrated multi-disciplinary subject spanning the science of materials, technology, engineering, health monitoring and simulation methods and algorithms for scrutinizing the assurance of reliable fusion reactor performance from the whole plant design phase through operation to decommissioning. Structural integrity is essential for maintaining high standards of public, environmental and investment protection and maximizing economic benefits. While fusion shares many of the structural integrity challenges faced by other industries, it also presents unique complexities. These include distinct regulatory requirements compared with fission, the need for innovative materials suited to extreme environments, advanced manufacturing techniques for component fabrication and the establishment of new facilities for technology demonstration, design verification and validation. Additionally, developing qualification processes, design rules, lifetime assessment methods, procedures, codes and standards is essential for verifying fusion reactor designs and predicting the lifespan of systems, structures and components. This paper reviews the challenges and advancements in fusion structural integrity, focusing on the tokamak concept and key in-vessel components: the breeding blanket and the divertor. It covers fusion regulations, operational environments, load cases, multi-material joints and the creation of fusion-specific design criteria. The paper concludes with a recommended pathway for future research, development and collaboration to advance commercial fusion energy. This article is part of the theme issue ‘Future challenges for structural integrity of high-integrity components’.

In order to optimize the high-speed milling parameters and reduce the experimental work in the actual processing, a multi-objective optimization model is established. The improved genetic algorithm NSGA-II combined with penalty function method is used to solve the mathematical model, and the optimal cutting parameters are obtained when the high-speed milling conditions are known, which provides guidance for the process decision-making of high-speed milling.

Martensitic stainless steels are widely used in industries due to their high strength and good corrosion resistance performance. Precipitation-hardened (PH) martensitic stainless steels feature very high strength compared with other stainless steels, around 3-4 times the strength of austenitic stainless steels such as 304 and 316. However, the poor workability due to the high strength and hardness induced by precipitation hardening limits the extensive utilization of PH stainless steels as structural components of complex shapes. Laser powder bed fusion (L-PBF) is an attractive additive manufacturing technology, which not only exhibits the advantages of producing complex and precise parts with a short lead time, but also avoids or reduces the subsequent machining process. In this review, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Then, the characteristics of defects in the as-built state and the causes are specifically analyzed. Afterward, the effect of process parameters and heat treatment conditions on mechanical properties are summarized and reviewed. Finally, the remaining issues and suggestions on future research on L-PBF of martensitic precipitation-hardened stainless steels are put forward.