激光粉末床熔融成形纯锌介观尺度熔池传热与流动机理研究(特邀)  

Heat Transfer and Flow Mechanisms in Mesoscale Molten Pool of Pure Zinc Fabricated via Laser Powder Bed Fusion(Invited)

作　　者：韩昌骏 袁道林 董志 黄金淼 吴潮潮 吴家柱[3] 杨永强[1] 王迪[1] Han Changjun;Yuan Daolin;Dong Zhi;Huang Jinmiao;Wu Chaochao;Wu Jiazhu;Yang Yongqiang;Wang Di(School of Mechanical and Automotive Engineering,South China University of Technology,Guangzhou 510641,Guangdong,China;School of Mechanical Engineering and Automation,Fuzhou University,Fuzhou 350108,Fujian,China;School of Mechanical Engineering,Guizhou University,Guiyang550025,Guizhou,China)

机构地区：[1]华南理工大学机械与汽车工程学院,广东广州510641 [2]福州大学机械工程及自动化学院,福建福州350108 [3]贵州大学机械工程学院,贵州贵阳550025

出　　处：《中国激光》2024年第20期152-162,共11页Chinese Journal of Lasers

基　　金：国家自然科学基金(52305358,52365041);广东省自然科学基金面上项目(2022A1515010304);中央高校基本科研业务费面上项目(2023ZYGXZR061)。

摘　　要：基于离散元方法和计算流体力学,建立了介观尺度下激光粉末床熔融(LPBF)成形纯锌熔池传热流动耦合模型,重点讨论了工艺参数对熔池温度场、流场演变以及熔道形貌的影响机制。研究结果表明:在LPBF成形过程中,低熔点低沸点的纯锌对瞬时热输入的变化非常敏感,随着激光功率增大,熔道成形尺寸、峰值温度、冷却速率均显著增加;当激光功率由30 W分别提高到60 W和90 W时,熔池的实时体积分别增长了510%和1730%;扫描速率的提高导致激光能量更多地被表层锌粉吸收,熔池的长宽比逐渐由1.28变为1.98,长深比由1.61变为3.45,熔池形态呈现长、浅、窄特征;熔深方向的温度梯度变大,最大冷却速率由3.6×10^(6)K·s^(-1)提高到1.3×10^(7)K·s^(-1);在高扫描速率下,实时熔池体积波动大,熔道成形具有不稳定性;随着激光能量密度增加,熔池内部流动不断加剧,激光中心区域的纯锌蒸发现象变得更加明显,熔池流动的主导驱动力逐渐由温度梯度引起的Marangoni对流转变为蒸发致反冲压力,熔道形貌逐渐由中心点状凹坑发展为连续的裂隙状。本研究结果可为LPBF成形过程中低熔点低沸点金属熔池演变研究与工艺优化提供理论指导。Objective Laser powder bed fusion(LPBF)additive manufacturing technology has been widely utilized to fabricate degradable zinc(Zn)implants and is a novel approach for creating complex structures with controllable shape and exceptional performance.However,printing Zn is challenging owing to its evaporative nature and narrow fabricating window arising from its low melting and boiling points.Therefore,a comprehensive investigation must be conducted to reveal the mechanisms of heat and mass transfer in molten pool during LPBF,which can provide theoretical guidance for the optimization of printing-process parameters.Methods A mesoscopic-scale heat transfer and flow coupling model of molten pool during the LPBF of pure Zn was established using discrete-element and computational fluid dynamics methods.Single molten-track experiments were designed to verify the numerical model.The mechanisms by which the process parameters affect the temperature field,flow field evolution,and morphology of the molten track were discussed.Results and Discussions Pure Zn is sensitive to changes in transient heat input owing to its low melting and boiling points.Increasing the laser power significantly alters the molten-track size,peak temperature,and cooling rate.Specifically,when the laser power is increased from 30 W to 60 W and 90 W,the real-time volume of the molten pool increases nonlinearly by 510%and 1730%,respectively(Fig.9).At higher scanning rates,more laser energy is absorbed by the surface of Zn powder,the length-width ratio of the molten pool changes gradually from 1.28 to 1.98,and the length-depth ratio changes from 1.61 to 3.45(Figs.4 and 5).Consequently,the molten pool is longer,shallower,and more narrow,thus resulting in larger temperature gradients along the direction of the molten-pool depth,with the maximum cooling rate increasing from 3.6×10^(6) K·s^(-1) to 1.3×10^(7) K·s^(-1)(Figs.6 and 7).Furthermore,the real-time volume fluctuated considerably and erratically during molten-track formation.As the laser energy den

关 键 词：激光粉末床熔融 纯锌 增材制造 数值模拟 传热流动耦合 

分 类 号：TN249[电子电信—物理电子学]