The rapid growth of additive manufacturing techniques requires a parallel tailoring and further development of already existing models applied to industrial solidification processes. Friendly modelling tools can be a valid aid in setting optimal operating parameters ranges for extending those modelling technologies to already existing or innovative alloys. A modelling approach is described simulating the generation of single tracks scanned over the powder bed in a selective laser melting process, attaining track geometry as a function of alloy thermophysical properties, laser speed and power, and powder bed thickness. Post-processing the model results allows for the derivation of the porosity of the printed part, due to lack of fusion, on one hand, and to yield conditions for the formation of porosities due to keyhole formation, on the other hand. The approach followed is based on a simplified representation of the physical aspects. Main simplifying assumptions concern the laser energy input, modelling the formation of the pool cavity, and modelling the powder bed thermophysical properties. In the model, the effective laser absorptivity that increases with rising specific energy is accounted for at the onset of vaporization to show the real trend of pool volume increase, the subsequent pool cavity deepening, and the laser ray’s interceptions. Modelling the effective laser absorption variation has been validated using literature experimental data relating to laser welding tests performed on 316L disks. The model has been adjusted using literature data providing measures of track width and depth and relative density of printed parts relating to different alloys: Ti6Al4V, Inconel625, Al7050, 316L, and pure copper. Few adjusting parameters are employed, namely: liquid pool effective thermal conductivity, slope of the effective laser absorptivity curve vs specific energy, and slope of laser energy application depth vs specific energy. Other checks on different alloys are needed to refine the adjustment; the results show good potential concerning the future possibility of using the model for achieving operating windows for alloys other than the tested ones, avoiding the need to provide experimental data specific for each alloy.

中文翻译：

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模拟金属粉末的选择性激光熔化

增材制造技术的快速发展需要对应用于工业固化过程的现有模型进行并行裁剪和进一步开发。友好的建模工具可以有效地帮助设置最佳操作参数范围，以将这些建模技术扩展到现有或创新的合金。描述了一种建模方法，模拟在选择性激光熔化过程中在粉末床上扫描的单轨道的生成，获得轨道几何形状作为合金热物理特性、激光速度和功率以及粉末床厚度的函数。对模型结果进行后处理，一方面可以推导出由于缺乏融合而导致的打印部件的孔隙率，另一方面可以为由于小孔形成而形成孔隙的条件提供。遵循的方法基于物理方面的简化表示。主要的简化假设涉及激光能量输入、池腔形成建模和粉末床热物理特性建模。在模型中，随着比能量的增加而增加的有效激光吸收率在汽化开始时被考虑在内，以显示池体积增加、随后池腔加深和激光射线拦截的真实趋势。使用与在 316L 盘上执行的激光焊接测试相关的文献实验数据，对有效激光吸收变化的建模已得到验证。该模型已使用文献数据进行了调整，这些数据提供了与不同合金相关的打印部件的轨道宽度和深度以及相对密度的测量值：Ti6Al4V、Inconel625、Al7050、316L，纯铜。采用的调整参数很少，即：液体池有效热导率、有效激光吸收率曲线对比能量的斜率、激光能量应用深度对比能量的斜率。需要对不同合金进行其他检查以细化调整；结果显示了使用该模型实现除测试合金以外的合金的操作窗口的未来可能性的良好潜力，避免了提供每种合金特定实验数据的需要。