Physics-based computational modeling and time-resolved imaging of plasma plume generated by nanosecond laser interaction with a bed of micro metallic powder
Physics-based computational modeling and time-resolved imaging of plasma plume generated by nanosecond laser interaction with a bed of micro metallic powder
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基于物理的计算建模和纳秒激光与微金属粉末床相互作用产生的等离子体羽流的时间分辨成像
DOI：
10.1016/j.addma.2022.102984
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发表时间：
2022
影响因子：
11
通讯作者：
Wu, Benxin
中科院分区：
文献类型：
--
作者：
Song, Hanyu;Liu, Weidong;Wu, Benxin
虽然连续激光器在选择性激光熔化或烧结中经常应用，但具有短脉冲持续时间的激光器（例如具有纳秒级持续时间的激光器）具有潜在的优势，这些优势可能包括良好的空间分辨率和小的热影响区。先前的工作已经报道了纳秒激光选择性激光烧结，特别是激光微烧结。在足够高的强度下，纳秒（ns）激光脉冲可以从其照射的金属粉末床表面产生等离子体羽流。等离子体羽流的演变，例如其在粉末床的表面上产生的压力，可显著影响粉末床中的烧结过程。然而，根据作者的知识，纳秒脉冲激光与金属微粉床相互作用产生等离子体的物理模拟工作在文献中还很少见到。这种建模工作已在本文中报道的~4-ns的激光脉冲与钴微粉床的相互作用，集成与时间分辨等离子体成像使用增强型CCD（ICCD）相机与纳秒级门宽度的模型验证。对于调查的条件下，模型预测的等离子体羽流的演变同意相当不错的ICCD成像结果为给定的一段时间的比较。这合理地支持了本文提出的假设（根据作者的知识很少测试）来自低于临界温度的金属微粉床的短ns激光脉冲诱导等离子体可以通过求解气相中的气体动力学方程以及求解粉末床凝聚相中的传热方程来合理地描述，其中耦合是通过Knudsen层（KL）关系在两相之间的界面处蒸发。模型计算表明，在与散装钴的情况相比，纳秒激光脉冲可以诱导更显着的表面蒸发从钴粉床，导致等离子体羽通常具有较高的峰值温度和密度在模拟期间。羽流可以在粉末床表面上产生峰值幅度约为491-MPa的短总压力脉冲。
Although continuous lasers see frequent applications in selective laser melting or sintering, lasers with short pulse durations (such as those with nanosecond scale durations) possess potential advantages that may include good spatial resolutions and small heat-affected zones. Previous work on selective laser sintering with nanosecond lasers has been reported, particularly for laser micro sintering. At a sufficiently high intensity, a nanosecond (ns) laser pulse can generate a plasma plume from its irradiated metallic powder bed surface. The plasma plume evolution, such as the pressure it generates on the surface of the powder bed, may significantly influence the sintering process in the powder bed. However, physics-based modeling work for plasma generated by nanosecond-pulsed laser interaction with a metallic micro powder bed has been seldomly seen in literatures according to the knowledge of the authors’. Such modeling work has been reported in this paper for a ~4-ns laser pulse interaction with a cobalt micro powder bed, integrated with time-resolved plasma imaging using an intensified CCD (ICCD) camera with nanosecond scale gate widths for the model validation. For the conditions investigated, the model-predicted plasma plume evolutions agree reasonably well with the ICCD imaging results for the given period of comparison. This has reasonably supported the hypothesis posed in this paper (which has been rarely tested according to the knowledge of the authors’) that a short ns laser pulse-induced plasma from a metallic micro powder bed below the critical temperature can be reasonably well described by solving gas dynamic equations in the gaseous phase together with solving the heat transfer equation in the powder bed condensed phase, where the coupling is via the Knudsen layer (KL) relations for vaporization at the interface between the two phases. The model calculations show that in comparison with the bulk cobalt situation, the ns laser pulse can induce more significant surface vaporization from the cobalt powder bed, leading to a plasma plume with typically higher peak temperatures and densities in the simulated period. The plume can generate a short total pressure pulse with a ~491-MPa peak magnitude on the surface of the powder bed.