The present work gives an insight into the microstructure evolution of AlSi7Mg produced by laser powder bed fusion and subjected to different heat treatment routes. Synchrotron powder diffraction and diffraction contrast tomography coupled with scanning and transmission electron microscopy investigations allowed an in-depth understanding of the effect of rapid solidification induced by laser powder bed fusion on material structure. In addition, the effects of solution treatment followed by water quenching and artificial aging and that of direct aging from the as built condition was investigated. The as built material exhibits the most important lattice contraction and the lower amount of Si phase, thus suggesting a higher content of solute Si, which decreases after artificial aging and after solution treatment. The eutectic Si is found in nanometric form, with crystallites of about 10 nm in size, which grow significantly after solution treatment. A similar behavior is also observed for the second phase β-Al₅FeSi. Traces of the π-Al₈FeMg₃Si₆ were observed after solution treatment. Direct aging induced the formation of a fine dispersion of β” precipitates in the primary Al solidification cells, which is responsible for material hardness and strength increase. The thermal treatments strongly affect the residual macrostrain, which is higher for the as built material and decreases after aging and solution treatment. This was confirmed by diffraction contrast tomography, which provided a spatial resolved structural information and was used as alternative tool to quantify the distribution of Si and Al phases.

本工作提供了对由激光粉末床熔合产生并经受不同热处理途径的AlSi7Mg的微观结构演变的见解。同步加速器粉末衍射和衍射对比断层扫描技术以及扫描和透射电子显微镜研究使得可以深入了解由激光粉末床熔合引起的快速凝固对材料结构的影响。此外，还研究了固溶处理后水淬和人工时效的影响，以及从建置条件直接进行时效的影响。建材显示出最重要的晶格收缩和较低的Si相含量，因此表明较高的固溶Si含量，在人工时效和固溶处理后，Si含量降低。发现共晶Si为纳米形式，具有约10nm尺寸的微晶，其在固溶处理后显着生长。对于第二相β-Al也观察到类似的行为₅ FeSi。的π-Al系的痕迹₈ FeMg ₃的Si ₆溶液处理后，观察到。直接时效会在初生的Al凝固孔中形成β”沉淀物的细分散体，这是材料硬度和强度增加的原因。热处理对残余大应变有很大影响，残余大应变对建材而言较高，在老化和固溶处理后降低。衍射对比层析成像技术证实了这一点，该技术提供了空间分辨的结构信息，并被用作量化Si和Al相分布的替代工具。