Composition variations induced by g-jitter in Bridgman growth of Sn-Bi alloys in microgravity

This work is a detailed analysis of the experimental data on g-jitter effec ts on solute segregation during directional solidification of tin-bismuth a lloys. The experiments were carried out under microgravity conditions withi n the framework of the MEPHISTO programme. The MEPHISTO data from the USMP- 3 space flight mission represented the first quantitative data on g-jitter effects on a directional solidification experiment that were obtained under well-defined conditions The growth conditions and the results of previous numerical simulations are briefly recalled, along with the predictions of a n analytical model for both the g-jitter induced composition variations and the time necessary to get back to steady state conditions. The feasibility of various mitigation strategies, aiming at counterbalancing the deleterio us effect of the g-jitters is also discussed. It is concluded that the abil ity of numerical modelling to provide reliable predictions of g-jitter effe cts for the interpretation and planning of future space experiments is stil l limited by a lack of well-documented experimental results that can be use d for verification. (C) 2001 Elsevier Science B.V. All rights reserved.