SOLIDIFICATION MICROSTRUCTURES OF METALS AND REFRACTORY ALLOYS ANALYZED IN THE GRENOBLE HIGH-DROP TUBE

Undercooling experiments have been performed on refractory materials b y processing in a high drop-tube. Emphasis is put on general aspects o f surface and bulk microstructures of solidified droplets, including p ure metals (W, Re, Ta, Mo, Nb, Ir, Zr) and alloys (W-Re, Mo-Re, Ta-Zr) . It is shown that recrystallization often causes polycrystallinity. M oreover, the microstructure is closely related to undercooling amount prior solidification. The effect of secondary cooling on microstructur e can also be studied by quenching the samples in solid tin at the end of free-fail.