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Expanding particle size distribution and morphology of aluminium-silicon powders for Laser Beam Melting by dry coating with silica nanoparticles
Journal of Materials Processing Technology ( IF 6.3 ) Pub Date : 2019-02-01 , DOI: 10.1016/j.jmatprotec.2018.08.045
Michael Cornelius Hermann Karg , Alexander Munk , Bhrigu Ahuja , Manuel Veit Backer , Jana Petra Schmitt , Christopher Stengel , Sergey Vyacheslavovich Kuryntsev , Michael Schmidt

Abstract Current requirements for metal powder in Additive Manufacturing via Laser Beam Melting in powder bed (LBM) that ensure repeatably homogeneous thin layers can be spread and LBM products with high relative density ρrel can be built are high sphericity and particle size distributions (PSD) with limited share of fine particles. The most established LBM powder production method today is delicate and costly inert gas atomization. It yields highly spherical particles with continuous particle size distributions, but two thirds of the atomized powder exceed established LBM size ranges. A novel process route to improve flowability of cohesive metal powders is the coating of micro-sized powder particles with small amounts of nanoparticles. In this article, significant improvements in powder layer smoothness and ρrel of LBM samples are shown by statistical analysis of physical experiments on the example of Al-Si powders dry coated with 0.5 wt% nanoparticular fumed silica SiOx. This setup was chosen because Al is most prone to powder flowability issues in LBM and no new chemical elements are added to the alloy from dry coated SiOx. Particle shape is varied from spherical over ovoidal to irregular using powder atomized with Ar, N and air. Effects of variations of PSD and LBM parameters on ρrel, defect types, microstructure and hardness using powders with and without SiOx are investigated. Because ρrel are skewed towards 100%, ANOVA on ranks is the applicable statistical method. Since the principle of using nanoparticles as spacers between microparticles is based on geometry, it is transferrable to other material systems. This may help for example to increase ρrel of LBM metal matrix composites prepared by mechanical alloying as non-spherical particles with considerable amounts of fine particles. The use of larger percentages of atomized powders in LBM can increase resource efficiency.

中文翻译:

用二氧化硅纳米粒子干法涂层扩大激光束熔化用铝硅粉的粒度分布和形貌

摘要 目前,通过粉末床激光束熔化 (LBM) 进行增材制造中金属粉末的要求是确保可重复均匀的薄层可以展开并可以构建具有高相对密度 ρrel 的 LBM 产品是高球形度和粒度分布 (PSD)细颗粒的份额有限。当今最成熟的 LBM 粉末生产方法是精细且昂贵的惰性气体雾化。它产生具有连续粒度分布的高度球形颗粒,但三分之二的雾化粉末超出了既定的 LBM 尺寸范围。一种提高粘性金属粉末流动性的新工艺路线是用少量纳米颗粒涂覆微米尺寸的粉末颗粒。在本文中,通过对涂覆有 0.5 wt% 纳米颗粒气相二氧化硅 SiOx 的 Al-Si 粉末的实例进行物理实验的统计分析,显示了粉末层平滑度和 LBM 样品的 ρrel 的显着改善。之所以选择这种设置,是因为铝在 LBM 中最容易出现粉末流动性问题,并且没有从干涂层 SiOx 中向合金中添加新的化学元素。使用用 Ar、N 和空气雾化的粉末,颗粒形状从球形、卵形到不规则形不等。研究了 PSD 和 LBM 参数变化对 ρrel、缺陷类型、微观结构和硬度的影响,使用含和不含 SiOx 的粉末。因为 ρrel 偏向 100%,所以等级方差分析是适用的统计方法。由于使用纳米粒子作为微粒之间的间隔物的原理是基于几何学的,它可以转移到其他材料系统。这可能有助于例如增加通过机械合金化作为具有大量细颗粒的非球形颗粒制备的 LBM 金属基复合材料的 ρrel。在 LBM 中使用更大百分比的雾化粉末可以提高资源效率。
更新日期:2019-02-01
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