激光粉末床熔融TC4钛合金熔道形貌及气孔形成机理研究  

TC4 Titanium Alloy Track Morphology and Pore Formation Mechanism in Laser Powder Bed Fusion Process

作　　者：齐士杰 熊林 陈明远 张纪奎 Qi Shijie;Xiong Lin;Chen Mingyuan;Zhang Jikui(Ningbo Institute of Technology,Beihang University,Ningbo 315800,Zhejiang,China;National Engineering Laboratory of Additive Manufacture for Large Metallic Components,Beihang University,Beijing 100191,China;School of Aeronautic Science and Engineering,Beihang University,Beijing 100191,China;Research Institute for Frontier Science,Beihang University,Beijing 100191,China)

机构地区：[1]北京航空航天大学宁波创新研究院,浙江宁波315800 [2]北京航空航天大学大型金属构件增材制造国家工程实验室,北京100191 [3]北京航空航天大学航空科学与工程学院,北京100191 [4]北京航空航天大学前沿科学技术创新研究院,北京100191

出　　处：《中国激光》2023年第12期228-236,共9页Chinese Journal of Lasers

基　　金：国家自然科学基金重大项目(52090044);国家自然科学基金面上项目(51775018);宁波市科技创新2025重大专项(2022Z014);北仑区关键核心技术攻关项目(2021BLG001)。

摘　　要：研究激光粉末床熔融工艺参数与熔道形貌、气孔缺陷的关联是优化工艺参数、提升成形效率的基础。使用不同激光功率成形TC4钛合金单条熔道,并建立基于流体体积法的气-液两相流三维细观熔池模型,对激光粉末床熔融增材制造过程中熔池内的传热、熔化、气-液两相流动等物理行为进行仿真分析。实验研究结果表明,随着激光功率由100 W增加至400 W,熔道深度大幅度增加,而熔道宽度只在较小功率(100~150 W)下随激光功率的增加而明显增大,此后(150~400 W)不再随功率变化而明显变化。同时,在大激光功率下(400 W)下,部分熔道底部可以发现不规则的气孔缺陷。熔池形貌的预测结果与实验结果的对比验证了仿真模型的有效性。仿真结果表明,随着激光功率增加,熔池底部在反冲力作用下形成匙孔,激光直接照射在熔池底部并使能量向下传递,表现为熔道深度明显增加,熔道宽度变化不明显。在高激光功率下,较深匙孔的底部呈“J”字形,其尾部不能直接受到激光作用,能量不足,易坍塌形成气泡,随后气泡滞留凝固形成气孔缺陷。Objective Compared with conventional fabrication methods,such as casting and forging,additive manufacturing(AM)presents high material utilization,outstanding mechanical behaviors,and near-net-shape fabrication;therefore,it has garnered considerable popularity in recent years.Laser powder bed fusion(LPBF)is common in metal AM and utilizes a scanning laser to melt parallel lines in each successive layer of powder,developing fine 3D structures with excellent material properties.The LPBF process exhibits a clear shortage in manufacturing efficiency,and numerous studies have been conducted to improve manufacturing efficiency by optimizing the process parameters.However,the design space of process parameters is limited because unreasonable parameters may lead to a lack of dimensional accuracy or internal defects.Therefore,studying the relationship between the process parameters and the quality of the formed parts is crucial.Most of the published studies focus on molten pools in“conduction mode”.The motion of“keyhole”mode molten pools,during which key-hole collapse may appear and lead to pore defects,still lacks sufficient investigation.In this study,experiments are performed to build the relationship between laser power and single-track morphology,thereby revealing the boundary of the parameter design space during the LPBF process.Furthermore,the key-hole motion behavior is exhibited with a finely built numerical model,and the formation mechanism of pore defects is analyzed.We hope this study will help in the optimization of LPBF process parameters and provide an academic reference for the analysis of pore defects.Methods TC4 powder was used as a starting material.First,single tracks were fabricated using the LPBF method at various laser powers.Then,the samples were sliced and polished,and the cross sections of the single tracks were characterized using an optical microscope(OM).Subsequently,the depth and width of the single tracks were measured,and the relationship between these dimensions and process paramete

关 键 词：激光技术 激光粉末床熔融 熔道形貌 工艺参数 数值模拟 气孔缺陷 

分 类 号：O439[机械工程—光学工程]