Titanium alloys are famous for their light weight, high strength, and heat- and corrosion-resistant properties. However, the excellent mechanical properties are closely related to its microstructure. Innovative machining operations are required for the welding, surface strengthening, and repairs to ensure the refining of the crystalline structure for improved strength requirements, enhanced mechanical properties, and integrating strength. By direct laser melting on the surface of Ti-6Al-4V alloy, the differences of molten pools under continuous and modulated laser mode were compared in the article. Under the same power, the heat influence zone of the laser pool could be reduced to 1/3 of that of the continuous laser. The deep molten pool could be obtained by a continuous laser by the action of high energy density. The tensile property changed a lot between different depths of melt penetration. A high-density, fine-grain molten pool could be obtained under the action of a high-frequency (20 kHz) modulation laser. The mechanical properties of the tensile sample between different depths of melt penetration, which contained the remelting zone, were close to the substrate. The research conclusions can provide technical support for the development of laser remelting processing technology.

In order to minimize the gaps between the direct laser deposition channels and improve the quality and performance of the formed parts, the process of direct laser deposition is utilized in laser additive manufacturing to create sequential, single- and double-channel deposition layers on 304 stainless steel plates. Under the premise of keeping the layer rate and defocusing amount unchanged, this study investigates the effects of laser power, scanning speed, and powder feeding rate on the morphology and inclusions of single- and double-channel deposited layers. The aim is to determine the optimal process parameter values for direct laser deposition of single-layer, single-channel Inconel 738. The effects of the three process parameters on the response values were investigated using a multi-factor, multi-level experimental design. The evaluation indexes for the analysis included the deposited layer wetting angle and aspect ratio. The analysis involved one-way extreme analysis and ANOVA analysis. The optimal process parameters are a laser power of 550~750 W, a scanning speed of 7~13 mm/s, and the powder feeding rate was 2.1~4.33 g/min. At the same time, the relationship between surface tension and gravity was integrated with the spherical coronal model and Young’s equation to develop a mathematical model of the direct laser deposition process at a theoretical level. The mathematical model of the direct laser deposition process was utilized to analyze the correlation between the geometric parameters of the cross-section of the deposited layer. This analysis provides a valuable data reference for future Inconel 738 direct laser deposition.

The effects of laser parameters on the microstructure and properties of plasma-sprayed yttrium oxide coating on the graphite matrix were investigated. Tensile strength, porosity, roughness, and scratch meter tests were carried out to evaluate the critical load and mechanical properties of the coating after spraying and laser micro-melting. When the porosity and surface roughness of the coating are minimum, the critical load of the coating is 7.85 N higher than that of the spraying surface. After laser micromelting, the crystal phase of Y₂O₃ coating surface does not change, the crystallinity is improved, and fine grain strengthening occurs. When the laser power density is 75 W/mm², the scanning speed is 30 mm/s, and the defocusing distance is 40 mm, the film base bonding performance and wear resistance of the material reach the maximum value. The failure of Y₂O₃ coating is mainly due to the degradation of mechanical properties such as film base bonding strength, surface porosity, and surface roughness, which leads to the local collapse of the material. The coating after laser micro-melting only presents particle disintegration at the end of the scratch area.

Laser cladding rapid solidification technique is an effective strategy for manufacturing ultra-high-strength martensitic stainless steels (UHS-MSS). Due to super-saturation solution strengthening of interstitial atoms (IAs), martensitic stainless steels containing IAs exhibit excellent ultra-high strength and toughness and have high tolerance for oxygen impurities. Hence, studying the specific speciation and structural characteristics of IAs is of great significance for guiding laser cladding of ultra-high-strength steels. Herein, we use density functional theory (DFT) computations to analyze the stable occupancies of IAs and their interactions in body-centered cubic iron (BCC Fe). The findings show that single IAs prefer to occupy octahedral sites over tetrahedral sites. Therefore, octahedral sites are selected as the optimal sites for the following double IAs study. For homo IAs, C-C and N-N configurations exhibit greater stability at long-range distances, whereas O-O demonstrate optimal stability at intermediate distances. Crucially, hetero IAs configurations are more stable compared to single IAs and homo IAs, exhibiting a synergistic effect. Especially, the C-O combination shows the highest stability and strongest bonding character. Meanwhile, the dissociation behavior of O indicates that C-O and N-O have higher dissociation temperatures than single O, further verifying the synergistic effect of hetero IAs. This provides a theoretical basis for understanding the interstitial solution strengthening of laser cladding UHS-MSS.

As nuclear energy expands, nuclear emergency response systems increasingly exhibit strong human–machine–environment (H–M–E) coupling, long-duration operations, and multi-department coordination, in which minor disturbances can be amplified by feedback loops into cascading failures and loss of situational control. To address the inability of conventional static and linear methods to represent dynamic risk evolution and chaotic uncertainty, this study proposes an integrated “risk network–chaotic evolution–synchronization control” framework. Based on 12-year-old on-site comprehensive drill reports from a Chinese nuclear power base, we construct a directed H–M–E risk network in a semi-quantitative, qualitative–quantitative manner and identify critical nodes using a composite betweenness–PageRank risk metric. We further abstract the system into a three-dimensional nonlinear coupled dynamical model; phase portraits, Lyapunov exponents, and bifurcation analysis confirm threshold effects, period-doubling routes, and chaotic attractors, revealing nonlinear amplification under strong coupling. Finally, an adaptive chaotic synchronization controller driven by network coupling strength is designed. Simulations show all strategies suppress chaos and achieve synchronization, while the machine-dominated strategy offers the best speed–energy trade-off for emergency resource allocation.