Solidification or hot cracks are commonly observed defects in a number of metal alloys and may lead to deterioration of additively manufactured parts quality. In this study, ultra-high-speed x-ray radiography experiments enable the observation and characterization of bundles of hot-cracks that form in monobloc AA6061 substrate. The crack bundles are related to meltpool characteristics and pore formation. Crack propagation rate is also presented for the case of a crack that initiates from a pore. Two types of relevant pore formation are also described, namely keyhole porosity and crack-remelting porosity. The results of this study are expected to facilitate the validation of theoretical and numerical models of solidification cracking.

凝固或热裂纹是许多金属合金中常见的缺陷，可能会导致加成零件的质量下降。在这项研究中，超高速X射线射线照相实验能够观察和表征在整体式AA6061基板中形成的热裂纹束。裂纹束与熔池特性和孔形成有关。对于从孔隙引发的裂纹，也给出了裂纹扩展速率。还描述了两种类型的相关孔形成，即锁孔孔隙度和裂纹重熔孔隙度。预期该研究的结果将有助于验证凝固裂纹的理论和数值模型。