Uniform distribution of BeO particles in Be casting produced in rocket free fall

Abstract

CAST beryllium is coarse-grained and, consequently, brittle. Much hot working is required to refine the grain structure of a cast beryllium ingot before good ductility is developed. Attempts at grain refining with for example, ultrasonics in the melt and stirring of the melt, have been unsuccessful. Research has also been undertaken (unsuccessfully) to find a grain-refining agent suitable for beryllium¹. A good grain refiner must be retained in the melt in the form of fine, dispersed particles. Particles in molten beryllium, however, because of its very low density, agglomerate and segregate from the melt terrestrially. This is believed to be due primarily to Stokes collisions and velocity gradient collisions. As the Stokes velocity is directly proportional to the acceleration due to gravity, the rate of agglomeration and subsequent segregation from the melt ought to be reduced considerably in the microgravity environment of space. We report here the results of an experiment in the weightless environment of space, using a sounding rocket equipped with the NASA electromagnetic containerless processing payload (ECPP), to melt and solidify a specimen of beryllium containing beryllia, an inoculant tried previously as a grain refiner.