RES ULTS FROM LOW-GRAVITY AND NORMAL GRAVITY EXPERIMENT 'TRACE+' ON DENDRITIC GROWTH AND THE COLUMNAR-EQUIAXED TRANSITION IN THE TRANS PARENT ALLOY SYS TEM NPG-DC

摘要

In 2011 the experiment "TRACE+" (Transparent Alloys in Columnar Equiaxed Solidification +) has been carried out onboard the sounding rocket TEXUS-49 in low-gravity environment. The experiment is a modification of the previous experiment "TRACE" on TEXUS-47. Both experiments aimed at investigating dendritic growth and the transition from columnar to equiaxed solidification in the transparent organic alloy system Neopentylglycol (NPG)-(D)Camphor (DC). As major difference the alloy concentration was changed from 37.5 to 20.0 wt.-% DC to investigate the concentration effect on the aforementioned phenomena. Furthermore some hardware improvements were carried out to enhance the image quality, as well as to increase the fluid flow amplitude on earth. All relevant experimental parameters like thermal gradient, solidification velocity and undercooling within the bulk liquid and at the columnar dendritic tips, as well as equiaxed grain density have been determined directly from the experiments. Here we present a summary of some of the experimental results of the TRACE+ experiment, including a comparison with reference experiments carried out under terrestrial gravity conditions. The results will serve as precise benchmark data for a comparison with different theoretical models.