OPTIMIZATION OF THE RHEOCASTING PROCESS UNDER CONSIDERATION OF THE MAIN INFLUENCE PARAMETERS ON THE MICROSTRUCTURE

摘要

The acceptance of the common thixocasting and rheocasting processes in the industry is, despite of several presentations of good structural part properties, still marginal. The main reason for this situation, regardless of plenty of research and several developments, is based on the complex experimental set-up, the cost intensive production and problems with the reproducibility. For a better acceptance of the semi-solid metal forming improvements in these fields have to be done. Research at the Foundry Institute of the Aachen University of Technology in the field of semisolid metals has a background of more than 15 years. The aim of this work is to concentrate on the main topics, which will lead to an acceptance of the process. To accomplish these demands on the process, we have designed several uncomplex experimental devices with no needs of electromagnetic reheating facilities and no other cost intense set-up equipments. The majority of the results were investigated in the so called "Cooling Channel Process", [1]. The development of the microstructure is based on forced nucleation by pouring the melt over a inclined channel and the decelerated cooling afterwards. Investigations were made on the main influences on the rheocasting process to improve the general knowledge of the process and to narrow down the boundary conditions. Further research was made on alternative processes for the production of semi-solid prematerial like the "Holding Process" [2], and the "Rheo Container Process (RCP)" [3]. All these processes have in common, that the formation of the microstructure is based on the nucleation during the casting process. In order to reject the cost intense reheating process, all investigated process routes work on the basis of "slurry on demand" production.