[en] Hot cracking is a known phenomenon during welding, which has a severe influence on the durability of aluminium alloys. The susceptibility of hot cracking plays a pivotal role in defining alloys weldability. Hot cracking mainly occurs at the mushy zone, this is the position between the solidus and liquation interface of the weld pool. The mushy zone is the region where the metallic alloy experiences thermal expansion and contraction. Over the years, many theories have been proposed to demonstrate and explain the solidification dynamics of the weld pool. However, these investigations are qualitative in nature. Meanwhile, many of the prediction models are not adequate due to the lack of quantitative information. For this reason, it is imperative for a reliable and robust quantitative forecast to evaluate and characterize some of the prevailing questions of hot cracking. Notably, how hot cracking correlates to welding parameters for its crack growth and cracks length. This research aims to introduce an in-situ observatory approach in the detection of hot crack formation and propagation during welding. The primary objective of this study was to develop a robust X-ray set-up with 40ms frame exposure at a frame rate of 10 frames/s during welding. This was achieved by using a conventional mini focus X-ray source (YXLON X-ray tube Y.TU 225-D04) and a 75 μm pixel size digital detector array (Dexela 1512). Sequential 2D radiographic projections were acquired for hot crack observation during single-pass gas tungsten arc welding. Five different aluminium alloys were investigated. In this study, a coplanar laminographic imaging system was used, which realizes a linear translation of weld material and detector together and parallel to the fixed X-ray source. This synchronized motion of the weld material and the detector allows penetrating the weld material with different exposure angles relative to the welding direction. Finally, the 3D information of the investigated weld material can be reconstructed by a coplanar laminographic reconstruction algorithm. The laminographic reconstruction algorithm was realized as a high-pass filter technique using a filtered back-projection algorithm with shift averaging of the related projections to generate a 3D laminographic reconstruction data of the weld region. A study of crack distribution was conducted by comparison of the acquired 2D radiographs of all the alloys used in the research. Furthermore, a crack distribution analysis was carried out to determine the relationship between crack initiation and crack propagation during welding. Temperature distribution measurements were taken from thermocouple elements and an infra-red camera. These were used to determine the temperature distributions and cooling rates at the mushy zone of the weld pool. Crack lengths and weld imperfections such as porosity and inclusions were measured by 3D-laminography and computed tomography reconstructions. The purpose of this research work was to develop an in-depth knowledge of the solidification cracking of aluminium alloys. This in-situ approach was also aimed to open new possibilities into the field of hot crack research by combining information on both the crack initiation and its correlation to the welding parameters.