The impact characteristics of a single shot are the fundamental indicators for studying the strength and coverage of mixed jet surface shot peening. The characteristics of the shot and the target material both have an impact on the crater characteristics after impact. This article uses 18CrNiMo7–6 low-carbon alloy steel after different heat treatments as the target material to study the crater characteristics under different shot impact conditions. Starting from the mechanism of crater formation, a single shot impact crater size model was established, and through experimental research, the error of high hardness target crater was corrected, reducing the prediction error of crater depth to less than 30%. On this basis, the laws of crater related characteristic parameters (depth to diameter ratio, proportion of crater diameter and crater depth, and ridge height) were studied. It was found that the hardness of shot particles and target materials had the most significant impact on the depth to diameter ratio and proportion of crater diameter and crater depth, while the ridge like structure around the crater only existed in low hardness target materials. The influence order of each parameter on ridge height is shot diameter, shot hardness, and shot velocity, respectively.

The application of non-contact laser ultrasonic technology in the metallurgical quality inspection and evaluation of laser additively manufactured (LAM) key metal components for aerospace has been widely studied and concerned. This technology can stimulate multi-mode ultrasonic waves by using a single pulsed laser excitation. Therefore, different metallurgical characteristics such as microstructures, defects, and residual stress can be detected and evaluated by analyzing the changes of characteristic parameters of ultrasonic waves in different modes. This paper focuses on the research progress of laser ultrasonic technology in detecting metal LAM defects, such as coarse grains, voids, cracks, and surface residual stress. The aim is to address challenges related to microstructural grain size assessment in strong-scattering material, online detection of micro-defects on rough surfaces, and high-precision characterization of surface residual stress under complex LAM environments involving high temperature, high pressure, and vibration. The main problems existing in the current research are analyzed. The results provide a reference for the future application of laser ultrasonic technology in the online detection of metal LAM metallurgical quality.

CuCrZr alloy complex structural parts were prepared by laser powder bed fusion (L-PBF). Under the optimum forming process parameters, the alloy samples with relative density of 99.65% were prepared, and the microstructure and properties of L-PBF forming samples in different directions were studied. The results show that the microstructure of XOY plane is equiaxed grains with different grain sizes. The microstructure morphology of the XOZ plane shows that the columnar crystal grows through the forming layer along the forming direction, the grain size is large, and there are semi-circular molten pools. The microhardness of XOY plane of CuCrZr alloy is higher than that of XOZ plane, and the tensile property of tensile samples at XOY plane and XOZ plane is slightly different. There are a large number of dimples in the tensile fracture morphology, which is a ductile fracture dominated by plastic deformation. The free electrons in the XOY plane are transmitted through the coarser columnar crystals, and the grain boundaries produce less scattering. The free electrons in the XOZ plane are transmitted through the equiaxed grains perpendicular to the forming direction, and the scattering effect generated by the grain boundary is large, so the electrical conductivity and thermal conductivity of the XOZ plane are lower than those of the XOY plane.

Aiming at the problem that the stress concentration at the sharp corners of lattice strut joints in conventional BCC lattice structures can lead to yield, this paper presents a design method of filleted BCC lattice structure (BCC-F) to reduce the stress concentration and ensure the structural safety for lattice structure. Validation was conducted through numerical simulation based on homogenization method and uniaxial compression tests on three groups of Ti–6Al–4V BCC and BCC-F lattice specimens. The results show that the filleted lattice joint can realize the geometrically smooth transition at the intersection of the lattice struts, and significantly improve the effective Young’s modulus and effective yield stress of the low-density BCC lattice structure, and change the failure mode of lattice structure. When the relative density of BCC and BCC-F were 0.327 and 0.370, the increase of effective Young’s modulus and effective yield stress of BCC-F were 142% and 64%, respectively, and the failure mode of BCC-F presented the characteristics of “multi-wave peak” collapse.

Residual stress induced cracking is still a bottleneck restricting the industrial application of laser melting deposition for large structures. Therefore, it is very important to explore the evolution law of residual stress and the microstructure correlation of residual stress – induced crack initiation and propagation in the process of laser melting deposition manufacturing of large components. Based on the fracture morphology analysis of large titanium alloy components and the macroscopic thermal-force coupling finite element calculation, the unique three-stage asymmetric cyclic loading mode of thermal stress during laser melting deposition is first found, namely, the stable cycle–burst loading stage, the nonlinear cyclic loading stage and the linear cyclic loading stage. The damage degree of three thermal stress loading modes on the unique basket structure of laser melting deposition is studied using coupled damage crystal plasticity simulation, and it is found that the linear cyclic loading mode is the most destructive, followed by the stable cycle–burst loading mode, and the nonlinear cyclic loading mode is the least destructive. This thermal stress loading mode, fracture morphology and microstructure analysis further show that the residual stress-induced cracking phenomenon is controlled by multiple factors such as excessive stress accumulation, geometric characteristics of parts, thermal stress loading mode and forming defects, rather than a single factor. It also provides a direction for systematic control of cracking from the aspects of timely stress relief, optimization of parts structure and process parameters, and reduction and suppression of defects.

The reproducibility of laser powder bed fusion (LPBF) technology in aerospace industry manufacturing is seriously affected by defects, and the defects in the powder spreading process have a significant impact on part quality. In this paper, a detection method based on the real-time semantic segmentation algorithm bilateral segmentation network (BiseNetV2) model and weighted loss is proposed for realizing category identification and location segmentation of powder spreading defects. In addition, a model pruning technique is utilized to optimize the size and performance of the deep learning (DL) model, and the lightweight model is deployed on computers in the monitoring system using the TensorRT technique. The results show that the BiseNetV2 model combined with weighted loss is able to detect five types of powder spreading defects with an average accuracy of 81.23%. The lightweight model obtained by pruning technique significantly reduces the model size by 13.39% while sacrificing 0.44% accuracy. Utilizing the TensorRT technique accelerates the deep learning model inference process and reduces the detection time to 5.94 ms with half-precision floating-point 16 (FP16) data.

Niobium alloys exhibit exceptional strength and lightweight advantages in the ultra-high temperature environment. However, conventional processing techniques face challenges in fabricating intricate components. In this study, two niobium alloys, Nb52 and Nb52 – 0.1ZrC, with dense microstructure, were prepared by selective laser melting (SLM) technology. The results show that the introduction of ZrC carbides significantly improves the strength of SLMed niobium alloys, and its yield strength, tensile strength, and plastic strain in the as-printed state reach up to 745.91 MPa, 795.45 MPa, and 1.8%, respectively. Fracture behavior at room temperature exhibits a combination of intergranular fracture and transgranular fracture modes. This work broadens the forming process of niobium alloy, and provides a new research idea for improving the properties of niobium alloys and developing a new low-cost niobium alloy system.

Using laser selective melting forming (SLM), casting, extrusion way prepared WE43 magnesium alloy specimens, through the Vickers hardness tester, density tester, optical microscope, scanning electron microscope, as well as tensile tester and other equipment to analyze the macro and microstructure and mechanical properties of the different preparation way forming WE43 magnesium alloy change rule. The models based on exponential function were designed to uniformly fit the stress–strain curves of WE43 with different forming methods, which laid a foundation for the future composite manufacturing of complex parts by additive, subtractive and equal material processes of WE43. The results show that SLM forming WE43 magnesium alloy has the highest strength, the tensile strength reaches 313 MPa, which is 183% of the casting state; extruded state of WE43 magnesium alloy has the best plasticity, the elongation rate reaches 10.2%, which is 232% of the casting state; the density of magnesium alloy of the SLM state is only 1.731 g/cm³, which is only 85.7% of the extruded state, and 95.2% of the casting state. The SLM state and the extruded state are ductile fracture, while the casting state is brittle fracture. SLM-formed WE43 has obvious anisotropy, the casting state and extruded state is not obvious. In the presence of a large number of hole-shaped defects around 20 μm, SLM-formed magnesium alloys still have the highest strength, mainly due to the average grain size of SLM-formed WE43 magnesium alloys of only 2.6 μm, the large amount of rare-earth phase precipitation present in the matrix, and the nanoscale sub-stable phases. It can be seen that the mechanical properties of the material can be significantly improved after welding and closing the internal hole-shaped defects in the SLM state magnesium alloy by further post-treatment methods.

In the aerospace area, automated fiber placement (AFP) has been widely used in the manufacture of complex-shaped composite materials. The C-beam is a typical example. The C-beam usually has a corner transition area with a large curvature. At the corner, it is difficult to ensure the placement quality and efficiency of the ±45° paths. In order to solve this problem, the influence on placement quality of the fiber number reducing method and the winding method is analyzed respectively. Furthermore, the advantages and disadvantages of the two placement strategies in the corner area are compared, and a comprehensive placement strategy is established. Finally, placement experiments are carried out on a C-beam and the results show that the comprehensive placement strategy can effectively ensure the placement quality and efficiency at the corner area of the C-beam.

With the development of national defense military and LED industry, the demand for sapphire substrates and the complexity of their shapes is increasing. Traditional polishing methods such as chemical mechanical polishing has the deficiencies of low efficiency and poor cambered-surface processing effect, while bonnet polishing, as one of the rapid polishing methods, is applicable to a variety of cambered surface polishing. Therefore, the bonnet polishing technology was applied to sapphire cambered-surface polishing. Firstly, the polishing motion model of sapphire was established on a robotic platform and the optimum processing parameters were obtained through single-factor test and orthogonal test. Then the polishing for the whole cambered surface was carried out under the optimum parameters and the effect of polishing time on the surface quality was investigated. The results show that the surface roughness Ra of the cambered surface reduces from 541.5 nm to 41.2 nm and the workpiece is conformal when the polishing time is 8 min, which verifies the feasibility of bonnet polishing for sapphire cambered surface.

To improve the surface quality of the exit edges of C/C composite holes, the value of the hole exit damage factor S_d (the ratio of the damaged area of the hole exit face to the ideal hole area after machining) is used as an indicator of hole exit quality. The grinding process parameters were optimized using single-factor and orthogonal test methods to analyse the hole exit edge grinding mechanism and propose a hole damage suppression strategy. The results show that when the spindle speed is 12000–14000 r/min, feed rate 5–7 mm/min, and ultrasonic amplitude 8–9 μm, the S_d value could be within 4.723×10^–3. The S_d value can be further reduced by 61.6% using the hole damage suppression strategy. Moreover, the S_d value of C/C composites under ultrasound-assisted grinding decreases and then increases with the increase of spindle speed and ultrasonic amplitude while gradually increases with increasing feed speed. When the optimum feed speed is ensured, increasing the spindle speed and ultrasonic amplitude will help to improve the surface quality of the hole exit and increase machining efficiency. The strategies of reducing the feed speed near the hole exit, using the side wall of the tool to smoothly grind the hole exit and adding an auxiliary support under the workpiece are effective in reducing hole exit damage.