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.

通过在激光熔化过程中对元素粉末进行原位合金化，可以克服开发新型合金，特别是用于激光粉末床熔化的挑战。该过程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，就粉末混合物的粒度分布和激光工艺参数研究了原位合金化的功效。Al-Cu 共晶体系的微观结构在这里用作粒子激光熔化过程中组成元素混合质量的指标。通过 α 或 θ 相的枝晶生长，很容易看到亚共晶或过共晶区域，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以一定范围的扫描速度和功率构建，以显示混合在不同加工参数下的影响。图像分析和维氏显微硬度测试均用于表征样品内的混合程度。这项研究的结果表明，由于粉末混合物中元素粉末的分离，可能会发生混合不良。当平均颗粒体积足够大以至于熔池包含太少的颗粒而不能作为混合物的随机表示时，这会产生不同于平均粉末成分的局部构建成分。熔池内的液相混合限制被认为不如熔池体积本身重要。