Three-dimensional (3D) reconstruction of the microstructure of Al – 7 wt.% Si samples solidified in microgravity conditions on board of the International Space Station was obtained from serial-sectioning images. The main objective was to quantify the number of dendrite fragments issued from the solidification process in absence of buoyancy force and with motionless dendrite fragments on contrary to ground-based experiments. The results show that the number of fragments strongly depends on the dendrite network configuration. More fragments are observed in the sample containing several dendrites with different orientations compared to a sample with well-aligned dendrites. . Moreover, it has been found that the highest number of fragments is mainly located in the region corresponding to an incipient grain boundary where dendrites with different orientations compete. Indeed, in this region solute accumulates and the microstructure is finer which is more prone to fragmentation of dendritic arms growing in this region. Thus, a mechanism that leads to the formation of dendrite fragmentation is identified: dendrite misorientation during solidification.

国际空间站上微重力条件下凝固的 Al – 7 wt.% Si 样品的微观结构的三维 (3D) 重建是从连续切片图像中获得的。主要目的是量化在没有浮力的情况下从凝固过程中发出的枝晶碎片的数量，并且与地面实验相反，枝晶碎片是静止的。结果表明，碎片的数量在很大程度上取决于树突网络配置。与具有良好排列的树突的样品相比，在包含多个具有不同方向的树突的样品中观察到更多碎片。. 而且，已经发现，最高数量的碎片主要位于与不同取向的枝晶竞争的初始晶界相对应的区域。事实上，在这个区域溶质积累并且微观结构更精细，更容易在该区域生长的树枝状臂碎裂。因此，确定了导致形成枝晶碎片的机制：凝固过程中的枝晶取向错误。