单晶连铸凝固过程中的组织演化

单晶连铸是一项新型金属型材制造技术。单晶组织的演化是在引晶初期通过晶粒的竞争生长机制完成的，晶粒的竞争生长过程依赖由传热条件决定的固液界面形状。本文观察了工业纯铝单晶连铸引晶初期的组织演化过程，并通过液淬观察了宏观固液界面形状与单晶演化速度的几何模型，讨论了铸锭尺寸，连铸速度及固液界面形状因子对单晶演化速度的影响。研究表明，铸锭尺寸越大，完成单晶演化所需时间越长，提高连铸牵引速度和界面形状因子，有

STRUCTURE EVOLUTION IN SOLIDIFICATION OF CCSC

The technique of continuous casting of single crystal metals ( C C S C) is a new type of continu ous casting . The structure of single crystalis formed at the initial stage of withdrawal. The m echanism ofstructure evolution is com petent growth of crystals which depends on the shape ofliquid/solid ( L/ S) inter face decided by the condition of heattransfer . In this paper ,the process of structure evolution of pure alu minum atthe initial stages of C C S C was experimentally investigated ,and the relationship of macro shape of L/ Sinterface with single crystal formation is analyzed through rapidly quench of the interface . The resultsshowed thatforming a convex interface is a necessary condition of single crystalform ation . A geo metricalmodelfor calculating the speed ofsingle crystal evolution was established ,by which the effects of casting di a meter,drawing speed and the shape factor of L/ Sinterface on the speed of single crystal evolution wereanalyzed . The results show ed that the bigger the casting ,the longer tim e for the single crystal evolution . Enhancing the withdrawalspeed and the shape factor of L/ Sinterface is of benefitto single crystal evolution . The theoretical calculation resultis identical with experimentalresult.