In order to predict the more accurate shape information of the melt pool in Selective Laser Melting (SLM), a new finite element temperature field simulations model is proposed. The simulations use a new heat source model that takes into account the influence of the powder layout, the surface of the substrate and the changes in the thickness of the powder layer after fusion on the energy distribution. In order to construct this new heat source model, firstly an improved optimization method based on the gradient descent and the univariate search technique is proposed to simulate the powder layout, and then the laser beam propagation between the powder and the surface of the substrate is tracked and recorded to obtain the energy distribution. Finally, according to the distribution of laser energy between the powder layer and the surface of the substrate, the heat source model is divided into two parts: one is the surface of substrate heat source model being the Gaussian distribution, the other one is the powder layer heat source model-satisfying the Gaussian distribution on the horizontal plane, changes in the depth direction according to the functional relationship obtained by the fitting. In addition, the thickness change of the powder layer after fusion is analyzed, and is taken into account in the heat source model. The powder simulation results are compared with the powder scattering experiment results to verify the effectiveness of the powder model. Comparing the temperature field simulation with the experiment, the results show that the predicted molten pool width relative error is 6.4%, and the connect width error is 9.6%, which has better accuracy and verifies the validity of the temperature field simulation model.
The surface-tension-driven Benard conventions and unique sub-grain cellular microstructures in 316L steel selective laser melting
在某些特殊合金（316 L、Al-Si、Co-Cr-Mo）的选择性激光熔化（SLM）过程中发现了独特的亚晶结构，亚微米尺度的胞状、拉长胞状甚至能带结构总是共存于单个宏观凝固晶粒内部。此外，蜂窝结构是对称的，具有六边形、五边形和正方形蜂窝图案，其中蜂窝尺寸仅在1μm左右。单层和散装316 L SLM实验，揭示了这些亚晶胞状组织的形成机制。在复杂的温度梯度和表面张力梯度的作用下，固/液界面（所谓的糊状区）前的局部对流和Bénard不稳定性形成了复杂的亚微米蜂窝状图案。换句话说，在S/L界面处发生的这种非线性自组织现象（Bénard不稳定性）叠加在宏观晶粒凝固过程上，以形成亚晶粒图案/结构和元素微观偏析。这种简单而统一的解释可以扩展到由SLM形成的其他共晶合金，如Al-Si系统。
Evaluation of the tribological properties of metal matrix composite materials (MMCs) obtained by additive manufacturing using selective laser melting (SLM)
The influence of Bi2O3 glass powder in silver paste on the fabrication of ohmic contacts and its potential effectiveness in solar cells and integrated circuits on p-type silicon substrates
Probing laser-driven surface and subsurface dynamics via grazing-incidence XFEL scattering and diffraction
European X-ray Free-Electron Laser Facility（欧洲X射线自由电子激光设施）；Department Physik, Universität Siegen（锡根大学物理系）；Helmholtz-Zentrum Dresden-Rossendorf（德累斯顿-罗斯多夫亥姆霍兹中心）；Department of Physics and Research Center OPTIMAS, RPTU University Kaiserslautern–Landau（凯泽斯劳滕-兰道理科大学物理系及OPTIMAS研究中心）
