脉冲激光辅助激光增材制造研究进展

Research Progress on Pulse Laser-assisted Laser Additive Manufacturing

针对辅助脉冲激光作用在固相区的情况,分别论述了非同步式表面、非同步式层间以及同步式脉冲激光辅助激光增材制造的工艺特点,分析了增材制造构件组织、成形缺陷以及应力分布的调控机理,并系统对比了非同步式和同步式脉冲激光辅助激光增材制造的调控效果,总结了同步式脉冲激光辅助激光增材制造的工艺优势。针对辅助脉冲激光作用在熔池区的情况,研究了脉冲激光功率密度、频率对熔池热动力学行为的作用机理(Marangoni对流、超声波搅拌空化、冲击波效应等),进而明晰了辅助脉冲激光冲击熔池对增材制造构件组织、成形缺陷的影响机理。最后,对脉冲激光辅助激光增材制造技术的研究进展进行了总结,并对下一阶段的发展方向进行了展望。

Laser additive manufacturing is an additive manufacturing technology that uses high-energy laser beams as a heat source to gradually form materials point by point and layer by layer with computer-assisted control.Typical laser additive manufacturing technologies include laser powder bed fusion and laser directed energy deposition.Among them,laser directed energy deposition technology can be used for component manufacturing,repair,and surface treatment.When used for surface treatment,it is also known as laser cladding technology.Compared with traditional manufacturing technologies,laser additive manufacturing reduces the reliance on molds and fixtures,enables rapid formation of complex components,shortens the product development cycle and manufacturing process,and has huge potential application demand in aerospace,automotive,biomedicine,and many other fields.However,during the laser additive manufacturing process,the high temperature gradient in the melt pool leads to a strong tendency for the solidification structure to grow epitaxially along the deposition direction.For example,the grain growth of titanium alloy formed by laser directed energy deposition can penetrate multiple deposition layers or even the entire specimen,resulting in anisotropy of the mechanical properties of the components.Additionally,the strong interaction between the laser and the material,as well as rapid solidification,lead to the formation of defects such as pores during the forming process.Furthermore,high residual tensile stresses are formed on the component surface,reducing the comprehensive mechanical properties of the formed components.In order to address these issues,scholars at home and abroad have attempted to improve the forming quality and mechanical properties of components by combining other technologies in the laser additive manufacturing process,such as electromagnetic field-assisted laser additive manufacturing,ultrasonic vibration-assisted laser additive manufacturing,and pulsed laser-assisted laser additive manufacturing.Among these technologies,the pulsed laser-assisted laser additive manufacturing is a non-contact composite manufacturing technology with advantages such as good processing flexibility and high controllability,which can effectively regulate the component structure,suppress formation defects,and improve residual stress distribution.In the process of pulsed laser-assisted laser additive manufacturing,the control mechanisms differ significantly depending on the target of pulsed laser action.This paper divides pulsed laser-assisted laser additive manufacturing into two cases:pulsed laser acting on the solid phase zone and acting on the melt pool zone.When pulsed laser acts on the solid phase zone,this technology is also known as laser shock peening-assisted laser additive manufacturing.Depending on the timing relationship between laser additive manufacturing and pulsed laser impact,it can be divided into asynchronous and synchronous laser shock peening-assisted laser additive manufacturing.The asynchronous type includes surface laser shock and interlayer laser shock.When pulsed laser acts on the melt pool zone,this technology is also known as pulsed laser shock melt pool-assisted laser additive manufacturing.This paper reviews recent research results from domestic and foreign sources for the cases where pulsed laser acts on the solid phase zone and the melt pool zone,respectively,summarizing the organizational,defect,and stress control mechanisms under different conditions.Finally,the research progress of pulsed laser-assisted laser additive manufacturing technology is summarized,and the future development direction is prospected.