外加物理场对激光熔化沉积内部缺陷控制

激光熔化沉积技术是基于“分层—叠加”原理，在高能激光束作用下、按照预定的路径，将同步送给的 金属粉末逐层熔化并快速凝固成形的先进制造技术，具有成形精度高、加工柔性好、内部组织均匀、力学性能 优异、适用难加工金属材料制备等优点，在航空航天等领域具有广阔的应用前景。但是激光熔化沉积过程中 容易产生未熔合、微裂纹、气孔等缺陷，限制了这项技术的大规模应用。其中，激光熔化沉积构件的微观组织 存在明显的各向异性，沉积过程中的快速加热和冷却使构件内部产生较大的残余应力从而导致其变形和开 裂。学者就如何改善激光熔化沉积构件的内部缺陷进行了广泛研究。因此，综述了通过在成形过程中外加温 度场、超声场、电磁场以及复合场的方法改善激光熔化沉积制件的内部组织和性能，以期为激光熔化沉积构件 综合性能的提高提供指导。

The control of internal defects during laser melting deposition by external physical field

Laser melting deposition technology is an advanced manufacturing technology based on the principle of layering-superposition. The metal powders sent synchronously are melted layer by layer and rapidly solidified according to the designed route, under the action of high-energy laser heat source. It has the advantages of high forming accuracy, good machining flexibility, uniform internal structure, excellent mechanical properties and suitable for the preparation of metal that difficult to machine. In consequence, it has a broad application prospect in aerospace and other fields. However, the large-scale application is limited by the defects such as lack of fusion, microcrack and pore, which are easily generated in the process of laser melting deposition. The microstructure of the laser melting deposited component shows obvious anisotropy and large residual stress exists because of the rapid heating and cooling during the deposition process, resulting in deformation and cracking. Many researchers have studied how to eliminate the internal defects of laser melting deposited components. In this paper, the methods of applying temperature field, ultrasonic field, electromagnetic field and compound field during the forming process to improve the internal structure and properties of laser melting deposited components are reviewed which may provide guidance for improving the comprehensive properties of laser melting deposited components.