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Laser additive manufacturing （LAM） enables the integrated direct formation of high-performance metallic components with complex geometry. However， the non-uniform distribution of temperature gradients， in-situ heat treatment effects， non-equilibrium solid phase transformations， and heterogeneous microstructure during the process result in intricate residual stresses that significantly affect the quality and overall performance. A comprehensive review of residual stress in LAM by introducing its fundamental definition and classification is provided in this paper. Furthermore， the particularity， formation mechanisms， characterization methods， and regulation techniques associated with residual stress in LAM is systematically reviewed. The subsequent sections introduce various characterization methods for residual stress in LAM components， along with their respective characteristics. Additionally， the applicability， advantages， and disadvantages of each method are presented. Furthermore， the methods for controlling residual stress can be categorized into post-treatment control and in-situ treatment control. Finally， the joint effect of different types of residual stress should be considered in the study of the cause and evolution mechanism of residual stress in LAM. The characterization method of residual stress should be integrated with various methods to facilitate mutual verification. To mitigate the impact of stress concentration on the printing process and resultant quality， as well as minimize the influence of post-processing stress on part accuracy， it is imperative to investigate in-situ control methods for residual stress and explore real-time online monitoring techniques for LAM.

In this work, a novel internal heat absorption technology using inorganic material rods is employed during the solidification process of steel ingots, aiming to control their solidification and improve the quality of the final product. The study investigates the effect of the insertion depth of inorganic materials on the solidification microstructure and macrosegregation of 2.5-ton 42CrMo ingots. The mechanical properties of samples from the product are also tested. A numerical simulation model for casting 2.5-ton ingots is established and implemented in Ansys Fluent fluid simulation software, with inorganic material rods set at different preset depths. The simulation explores the physical processes of the melting and floating of inorganic materials in molten steel, as well as their effects on the temperature and flow fields of the material. The results show that deeper insertion of inorganic materials (200 mm from the hot top) reduces the tendency for macrosegregation compared to that at the insertion depth of 100 mm. Specifically, the positive segregation area decreases by 10.35%, while the negative segregation area decreases by 15.32%. Moreover, deeper insertion results in a significant refinement of the solidification microstructure, ultimately enhancing the mechanical properties of the products machined from the ingots (i.e., the yield strength increased by 4.7%). The numerical simulation results indicate that as the placement depth of inorganic materials in the ingot mold increases, the cooling effect becomes more significant, the flow area of molten steel initiated by the inorganic materials expands, and the linear velocity of the double-circle flow increases. This further explains why the solidification quality of the ingots improves with the increasing placement depth of inorganic materials. [ABSTRACT FROM AUTHOR]