Qiuping Wang

The laser powder bed fusion (LPBF) technique is used to manufacture complex and customised components by exploiting the unique advantages of two types of metal materials to meet specific performance requirements. A comprehensive overview of LPBF-processed dissimilar metal materials, a combination of different single metals or alloys, is developed. The microstructure in the fusion zone and the corresponding mechanical properties of LPBF-processed dissimilar metal materials are summarised. The influence of processing factors on the mechanism of defect formation, wetting properties and element diffusion behaviour at the interface between different materials and their typical cases are scientifically investigated in detail. Particular attention is paid to energy input, Marangoni convection and interfacial bonding behaviour. The underlying science of the metallurgical structure and properties of the LPBF-processed dissimilar metal materials is revealed. The build quality and efficiency could be further improved by designing machine structures and predicting the process–property relationship. This review provides a significant guide for expanding the industrial application of LPBF-processed dissimilar metal materials.

The mold filling of semi-solid slurry involves intricate theory and physical phenomenon. The influence of inner gate shape and filling speed on free surface and liquid-solid distribution is investigated by adopting finite element numerical simulation. The effect of viscosity is considered in the modelling. The results show that the inner gate shape affects the free surface. The filling speed of 3 m/s is favorable for the uniform distribution of solid-liquid phases. It has important guiding significance for the optimization of semi-solid forming process and molding design.

To improve the calculation efficiency and to avoid the updating results being affected by optimization algorithms, a direct calculation of updating parameters method based on Kriging model for model updating is proposed in this paper. The proposed method first generates the data samples of updating parameters by using Latin hypercube Design (LHD). The corresponding structural response is calculated by initial finite element model. Then, the explicit function between updating parameters and structural responses is obtained based on kriging theory. Finally, the best design parameters are directly solved using the experimentally obtained structural response as the objective value based on the established Kriging model. Model updating of Caiyuanba Yangtze River Bridge is employed to test the proposed method. The results show that the model updating based on direct calculation method avoids the iterative calculation and improves the computational efficiency. The proposed method can provide the approximate accuracy level compared with the traditional Kriging model method.

XTiB2/Al-20%Si composite is a hypereutectic Al-20Si alloy containing x wt% TiB2 sub-micron or nanometre level in situ particles. The xTiB2/Al-20%Si composites were prepared using an 11% TiB2/Al-6Si composite as the master alloy. The phases and microstructures in the composites were evaluated by use of XRD, OM, SEM, EDS, EPMA, and TEM. The microstructural evolution of the Al-20Si alloy with the addition of TiB2 particles from 1 wt% to 6 wt% was investigated. The results showed that the primary Si, α-Al phase, and eutectic Si could be refined and modified by TiB2. Meanwhile, the crystal structures of Ti-B compound enwrapped by primary Si and α-Al phase were identified and analysed and found to form a close-packed hexagonal structure. Compared with the microstructures of composites containing different amounts of TiB2, the TiB2 particles played an important role in the nucleation of primary Si and the growth of primary Si, eutectic Si, and α-Al phases, also explaining the mechanism underpinning the effect of TiB2 on the nucleation and growth of Si and α-Al phases.

The unidirectional isothermal compression experiment of semi-solid CuSn10P1 alloy was carried out by Gleeble 3500 thermal simulator. The effects of different deformation parameters on the microstructural evolution were investigated. The results show that the deformation process is accompanied by dynamic recovery and dynamic recrystallization. During the unidirectional isothermal compression experiment, when the strain rate is reduced, the deformation duration is prolonged, generating a high dynamic recrystallization nucleation rate. When the strain capacity increases, the internal deformation storage energy and dynamic recrystallization nucleation rate all increase. The distribution of Sn element during deformation process has a great influence on dynamic recrystallization, and the recrystallization is preferentially nucleated at location where the content of Sn element is high. According to TEM analysis, the recrystallization mechanism of Cu-Sn alloy at low temperature and strain rate is continuous dynamic recrystallization dominated by subgrain merging and rotation.