Crystallization of Silver‐Germanium Alloys under Microgravity I. Eutectic Crystallization in Hypoeutectic Alloy

Abstract

The results of a study on eutectic crystallisation in the hypoeutectic alloy under different convection conditions are presented. Buoyancy driven convection was suppressed by processing the samples under microgravity conditions. The effect of convection level on the eutectic crystallisation is shown to be significant: In the absence of convection, the non-equilibrium level of the process is enhanced. The characteristic dependence of the particle size on the distance from the surface of a sample, observed on the minor phase of the eutectic, is discussed.Dam cet article nous prkntons les rbultats d'une etude sur la crystallisation eutectique d'un alliage hypoeutectique sous diffhrentes conditions de convection du flux. Nous avons supprim6 la convection dirigees par la poussee en realisant les echantillons sous microgravite. L'effet du niveau de convection sur la crystallisation de l'eutectique est remarquable. En supprimant la convection nous nous eloignons davantage de l'etat d'equilibre. Nous discutons les raisons possibles de la dependance de la taille des particules en fonction de leur distance par rapport a la surface. IntroductionThe presented work is part of a systematic study on the solidification process of multiple-component melts under different convection conditions. Both the typical anomalous behaviour of the Ag-Ge eutectic system and the significant sensibility of eutectic solidification to the external conditions were the reasons for the Ag-Ge system to be chosen as an appropriate model material.A number of authors has studied the crystallisation process in the absence of buoy-