Solidification of Hypermonotectic Al-In Alloys Under Micro-Gravity Conditions
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MATERIALS PROCESSING IN THE REDUCED GRAVITY ENVIRONMENT OF SPACE
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Guy E. Rindone, editor SOLIDIFICATION OF HYPERMONOTECTIC GRAVITY CONDITIONS
Al-In ALLOYS UNDER MICRO-
CLAUDE POTARD C.E.N.G., Laboratoire d'Etude de la Solidification, France
85 X, 38041 Grenoble Cedex,
ABSTRACT Four samples of the Al-In system having monotectic and hypermonotectic compositions were solidified under microgravity during the NASA-SPAR IX flight of January 20th,1981. The experimental thermal and physico-chemical conditions actually achieved have been analysed. Radiographic and metallographic observations of the samples show a non-regular dispersed primary phase inside the monotectic matrix. These observations are commented on the basis of capillarity and solidification aspects.
KEYWORDS Liquid miscibility gap alloys; solidification; microgravity: aluminiumindium alloys.
INTRODUCTION This report presents the preliminary analysis of the experiments performed during the SPAR IX flight of January 20th, 1981. The purpose of this work is to describe the observations made on the four flight samples, to connect these observations to the achieved experimental conditions and to compare them to ground-based test results.
RECALL OF OBJECTIVES AND DESIRED EXPERIMENTAL CONDITIONS The general objective of this research program is to obtain regular dispersed solid structures of hypermonotectic composition using weightlessness. Within this objective, the analysis of the mechanisms involved in the structure formatask of the research program. tion constitutes the first The conditions chosen for this purpose were based on - the control of capillary interactions between the existing phases, - the purity of the media, states and heat treatment processes. - well-defined initial These conditions and their expected consequences on the behaviour of the alloys and the experimental method have been well described in earlier works [1,2]. Only a short summary will be presented here : 0 The homogeneous Al-In. 1 0 liquid alloy held at 900 C in a Silicon Carbide Crucible is progressively cooled down until solidification during the microgravity period of the rocket flight. By this process, a dispersion of indium-rich liquid phase (indium phase) should be created within an aluminium-rich liquid matrix. A controlled solidification stage is the method chosen to keep the dispersion in the solid state. The General Purpose Rocket Furnace build by NASA/MSFC was used in gradient solidification mode.
544 Two cartridges each containing two samples were processed under different conditions : - the cartridge NR 76-51/1 was treated under directed heat flow with a low thermal gradient ("Low G" cartridge). - the cartridge NR 76-51/2 sustained directed heat flow with a higher thermal gradient ("High G" cartridge). Two thermocouples located on the lid of the upper crucible (Mid.TC) and on the bottom of the cartridges (Bot.TC) measured the temperatures applied to the samples. data for the two experiments. Table 1 summarizes the initial
TABLE 1 Flight cartridges : ini
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