粉末粒径分布对SLM-GH3536合金熔池形态的影响

Effect of powder particle size distribution on the molten pool morphology of SLM-GH3536 alloy

激光粉末床增材制造过程通常采用离散元法和计算流体力学相结合的方式对熔融过程进行仿真分析。离散元生成粉末床的质量一定程度上依赖于试验测量的粒度分布数据,通常采用离散的试验测量结果来建立粉末床,不利于对粉末分布形式进行推广。本文针对GH3536合金粉末的激光选区熔化(selective laser melting,SLM)成形过程进行热流耦合仿真,建立了单层单道扫描的三维热流耦合模型。以均匀分布的粉末床为基准,对比了试验测量的离散分布以及近似的对数正态分布粉末床对应的熔池形态差异以及成形效果。结果表明虽然近似的对数正态分布粉末床整体的熔池形貌不如试验分布,但是从外观上看过渡更加均匀,而且仅需要均值和方差信息就可以确定粉末分布形式,这说明近似的概率分布形式虽然与实际情况存在一定差异,但是便于建模和参数分析。此外,本文通过调整激光功率和扫描速度的组合,分析了不同参数组合下熔池轨迹的变化规律。结果表明在能量输入接近的条件下,较低的激光功率和扫描速度具有更好的成形效果。本研究对激光选区熔化成形GH3536合金的仿真建模以及制粉过程有一定的指导作用。

Laser powder bed fusion additive manufacturing is commonly modeled and analyzed through a hybrid application of the discrete element method and computational fluid dynamics.The efficacy of discrete element method in generating powder bed is contingent upon experimentally measured particle size distribution data,yet translating these distributions from experimental measurements into generalized forms for powder bed is challenging.This research presents a thermalfluid coupled simulation of the selective laser melting(SLM)process applied to GH3536 alloy powder,constructing a three-dimensional model for the thermal-fluid dynamics involved in single-layer,singletrack scanning.By using a uniformly distributed powder bed as a reference,the study contrasts resulting melt pool morphologies and associated forming effects between the beds with experimentally measured discrete distributions and those approximating a log-normal distribution.The results show that the molten pool shapes in the latter are visually more uniform,despite not matching the quality of the experimentally derived distributions.Intriguingly,defining the powder bed distribution required only mean and standard deviation data suggesting that despite observable deviations,such an abstracted probabilistic distribution is practical for modeling and analytical purposes.Additionally,the paper investigates how molten pool tracks are influenced by variations in laser power and scanning speed,analyzing outcomes across an array of parameter settings.It was observed that lower laser power and scanning speed yield improved formation quality when energy input is held consistent.This study can provide certain guidance for the simulation modeling of the selective laser melting forming process as well as the powder-making process for GH3536 alloy.