Efficacy of elemental mixing of in situ alloyed Al-33wt%Cu during laser powder bed fusion
Efficacy of elemental mixing of in situ alloyed Al-33wt%Cu during laser powder bed fusion
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DOI：
10.1016/j.jmatprotec.2021.117379
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发表时间：
2022-01
影响因子：
6.3
通讯作者：
J. Skelton;E. Sullivan;J. Fitz-Gerald;J. Floro
中科院分区：
文献类型：
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作者：
J. Skelton;E. Sullivan;J. Fitz-Gerald;J. Floro
开发新型合金，特别是用于激光粉末床熔合的新型合金的挑战可以通过在激光熔化期间原位合金化元素粉末来克服。该工艺可以加快各种合金成分的原型制作，并减轻制造定制合金粉末的限制和成本障碍。在这项研究中，原位合金化的功效进行了研究相对于粉末混合物的粒度分布和激光工艺参数。Al-Cu共晶系统的显微结构在此用作在颗粒的激光熔化期间组成元素的混合质量的指标。通过α或θ相的枝晶生长，可以很容易地看到低共熔或过共熔区域，这表明溶质浓度偏离标称共晶成分的区域。样品由四种粉末混合物在一系列扫描速度和功率下构建，以显示在不同加工参数下如何影响混合。图像分析和维氏显微硬度测试都用于表征样品内的混合程度。该研究的结果表明，由于粉末混合物中元素粉末的分离，可能发生混合不良。当平均颗粒体积足够大使得熔池包含太少的颗粒而不能作为共混物的随机表示时，这产生不同于平均粉末组成的局部构建组成。液相混合池内的限制被认为是不太重要的熔池体积本身。
Challenges in developing novel alloys, specifically for use in laser powder bed fusion, may be overcome by in situ alloying of elemental powders during laser melting. This process could expedite prototyping of various alloy compositions and alleviate the restrictions and cost barriers of creating custom made alloy powder. In this research, the efficacy of in situ alloying is studied with respect to particle size distributions of the powder blends and the laser process parameters. The microstructure of the Al-Cu eutectic system is used here as an indicator of mixing quality of the constituent elements during laser melting of the particles. Hypo- or hypereutectic regions are readily visible through the dendritic growth of the α or θ phases, indicating regions where the solute concentration deviates from the nominal eutectic composition. Samples were built from four powder blends at a range of scan speeds and powers to show how mixing is affected at different processing parameters. Image analysis and Vickers microhardness tests are both used to characterize the degree of mixing within the samples. Results of this study show that poor mixing can occur due to segregation of elemental powder within the powder blend. This produces local build compositions different than the mean powder composition when the mean particle volume is large enough that the melt pool encompasses too few particles to be a stochastic representation of the blend. Liquid phase intermixing limitations within the pool are thought to be less important than the melt pool volume itself.