Papers by Author: U. Hecht

Abstract: The preparation of the solidification experiments planned onboard the ISS within the SETA research program was supported by a first full test run within the SQF- Solidification and Quench Furnace of the Materials Science Lab (MSL) using an eutectic alloy of the Al-Cu-Ag system as test sample. This first SCA prototype test in the SQF comprises a directional melting, solidification and subsequent quenching of the sample. The test evaluation presented in this paper is limited mainly to the evaluation of the recorded sample temperatures and focuses on the experimental performance in the view of a scientific user of the SQF. The thermal gradient achieved in the sample reaches about 10.6 K/mm and showed a good stability over the pulling length. The position of the solidification interface relative to the middle of the adiabatic zone, however, is shifted considerably towards the cooling zone. The quenching performance reached a starting value of 27 K/s.

Abstract: Coupled, regular eutectic growth of α(Al) and Al2Cu from ternary Al-Cu-Ag liquid alloys is investigated with focus on the formation and the characteristics of eutectic cells in unidirectionally solidified, polycrystalline, bulk samples. The topologic anisotropy of the lamellar eutectic leads to destabilization along the lamellae with elongated cells being intermediate to stable cells, irrespective of the crystallographic orientation of the phases. The formation of stable cellular patterns with elongated or regular cell structure is explained with reference to the crystal orientation of the phases α(Al) and Al2Cu, measured by electron backscatter diffraction (EBSD).