目的 从宏观工艺配置角度探究介观尺度下单道与多道仿真模型的温度特征、表面特征以及缺陷特征,进而通过建立“工艺配置-物理特征-缺陷演变”三元映射模型,为轨迹缺陷的有效调控提供理论支持。方法 首先采用预实验结合有限体积法建立并校正介观尺度高保真数值模型,并以激光功率、扫描速度以及扫描间距为变量设计仿真与实验方案,进而探究单、多道零件成形过程中熔池特征、温度演化、表面形貌及其形成相关缺陷的演变规律。结果 熔池在成形过程中出现圆形-椭圆形-彗星状的演变倾向;在多道成形中,先前打印层对周围粉末床的预热作用可将后续打印中熔池寿命从132.3 µs显著提升至174.3 µs,进而提高成形稳定性;不同激光功率P、扫描速度v和扫描间距m配置下的成形轨迹存在较大差异,在线能量密度150~ 350 J/m范围内,熔池宽度与线能量密度间表现出正相关;在P=320 W、v=1.05 m/s,m=70 µm的参数组合下,轨迹上表面表现出理想形貌。结论 通过对熔道和熔池表面形貌进行观察分析,发现该数值模拟模型与实验结果相吻合。此外,不同工艺参数的配置直接影响了热输入的分布,进而影响了熔池动力学行为,因此,合理优化工艺参数配置,可以在提高成形精度的同时,改善表面质量、减少缺陷,确保最终产品的性能和可靠性。
Abstract
The work aims to investigate the thermal properties, surface attributes, and defect characteristics of single-track and multi-track simulation models at the mesoscopic level, with a focus on the overarching macroscopic process configuration, and establish a ternary mapping model of “process configuration-physical characteristics-defect evolution” to provide theoretical support for the effective regulation and control of trajectory defects. Initially, a high-fidelity numerical model at the mesoscopic scale was developed and refined through the integration of preliminary experimental data and the finite volume method. Subsequently, simulation and experimental protocols were formulated with laser power, scanning speed, and scanning spacing as variable parameters. Then, the study investigated the evolution laws governing the characteristics of the molten pool, the progression of temperature, surface morphology, and the development of associated defects during the fabrication process of both single and multiple components. The findings indicated that the molten pool demonstrated a progression characterized by circular, elliptical, and comet-like shapes throughout the formation process. Furthermore, the preheating influence of the preceding printed layer on the adjacent powder bed during multi-pass formation could substantially extend the lifespan of the molten pool in subsequent printing stages, increasing it from 132.3 µs to 174.3 µs, which in turn enhanced the stability of the forming process. Variations in laser power (P), scanning speed (v), and scanning spacing (m) resulted in notable differences in the formation trajectories. Nevertheless, within the specified range of line energy density from 150 to 350 J/m, a positive correlation was observed between the width of the molten pool and the line energy density. With the parameter settings of P=320 W, v=1.05 m/s, and m=70 µm, the upper surface of the trajectory exhibited an optimal morphology. The numerical simulation model demonstrates a significant degree of alignment with the experimental findings, as evidenced by the observation and analysis of the surface morphology of both the melt track and the melt pool. Variations in process parameter configurations have a direct impact on the distribution of heat input, which in turn affect the dynamic behavior of the molten pool. Consequently, a judicious optimization of these process parameters can significantly enhance the accuracy of the forming process, improve surface quality, minimize defects, and ensure the performance and reliability of the final product.
关键词
选区激光熔化 /
表面形貌 /
温度演进 /
工艺参数 /
熔池特征
Key words
selective laser melting /
surface morphology /
temperature evolution /
process parameter /
melt pool characteristics
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基金
国家资助博士后研究人员计划（GZC20250943）; 长安大学中央高校基本科研业务费专项（300102255101）; 陕西省2020年自然科学基础研究计划（2020JQ-380）
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