Based on calculating the thermal history and the gravity level of some metallic droplets during their dropping in drop tube under different conditions, the limitation of drop tube investigation on microgravity was analyzed and discussed. In order to solve the problem that the effects of microgravity and undercooling were usually coupled and difficult to distinguish, some liquid metals with low melt points, low radiant emissivities and relative high specific heats, such as A1 and Cu alloys, were quenched into silieone oil before and after falling. The difference of microstructures between the both conditions was analyzed both theoretically and experimentally. The results showed that this way could make the temperature difference of droplets before and after falling to be neglected, and thus the microgravity effects on alloy solidification would be much more conspicuously identified. Therefore, the extent of material investigations by drop tubes was expanded.
修改评论