In recent years, additive manufacturing technology has developed very rapidly and has been widely used in aerospace, biomedicine and other fields. Among them, laser selective melting forming technology can directly manufacture high-performance metal parts from CAD models and metal powder/wire. Its workflow can be summarized as follows: First, use 3D drawing software on the computer to design the 3D model of the part, and then convert it into The STL file is sliced ??according to a certain layer thickness to generate a two-dimensional laser processing trajectory. The equipment pre-lays/coaxially inputs the metal powder based on the generated processing trajectory. After the scanning is completed, the substrate is lowered to a certain depth and the process is repeated until the part is completed, layer by layer to complete the preparation of the entire metal part.
Because laser selective melting forming technology has the characteristics of small spot and high cooling rate, the formed metal parts have fine structure, high precision and good performance. It is especially suitable for thin walls, complex inner cavities, internal flow channels, etc. The overall manufacturing of complex precision components that is difficult to achieve with traditional processing technology. However, the following metallurgical defects still exist during the forming process: (1) The temperature gradient is large and the cooling rate is fast during the forming process, which generates excessive thermal stress, resulting in deformation or cracks during the forming process; (2) Holes are easily generated during the forming process ; (3) Based on the bottom-up temperature gradient along the forming direction, the microstructure usually grows in the form of columnar crystals and produces texture, resulting in anisotropy in its properties.
Based on this, researchers at home and abroad have currently carried out a series of studies. For example, patent CN104195541A discloses a method and device for electromagnetic composite field collaborative laser cladding. By controlling the Lorentz force To control the flow of the molten pool, achieve the purpose of regulating the solidification structure, optimizing the mechanical properties of the workpiece, and improving the morphology of the cladding layer. However, due to the extremely short laser action time, the effects of tissue homogenization and grain refinement are not obvious. Another example is patent CN106350817A, which discloses a method and device for preparing a crack-free cladding layer by ultrasonic vibration-assisted laser cladding. The ultrasonic vibration aging is directly introduced into the molten pool micro-area, and the direct cavitation effect, mechanical effect and thermal effect of the ultrasonic wave are used to promote The stress field of the cladding layer is uniformized, the grain structure is refined, and the occurrence of cracks is suppressed from the root. However, the existence time of the liquid molten pool during the laser cladding process is very short, and the effect of ultrasound on the cladding layer is not very significant. Another example is patent CN 105714284 A, which discloses a method and device for ultrasonic vibration-electromagnetic stirring composite energy field-assisted laser cladding. It can effectively improve the shortcomings of the small range of ultrasonic treatment and the insignificant refinement effect of electromagnetic stirring. However, laser Cladding is just a thin cladding layer with a simple two-dimensional shape and a single scanning method. Laser selective melting and forming is a layer-by-layer accumulation process. Each layer has a different two-dimensional shape and the scanning method is complex. It cannot be combined The methods and equipment used in laser cladding need to be redesigned according to the characteristics of laser selective melting when they are transplanted into laser selective melting.