A Novel Directional Solidification of TiAl-Based Alloys by Electromagnetic Cold Crucible Zone Melting Technology with Y 2〇3 Moulds

摘要

In order to decrease mould contamination, a novel directional solidification process was developed for TiAI-based alloys, where an Y2O3 mould was incorporated into electromagnetic cold crucible (EMCC) zone melting technology. To determine the characteristics o f this process, the macro/microstmctures and mechanical properties o f directionally solidified (DS) Ti^45Al-2Cr-2Nb ingots prepared by two kinds of directional solidification techniques, namely traditional graphite heating (control group) and EMCC heating, were extensively investigated using electromagnetic field and temperature field. Compared with the control group, this new technique can induce bigger electromagnetic force in the tangential direction, generate a more rapid heating and higher temperature gradient, and decrease the interaction between the mould and me however the heat transfer is altered to inclining outward owe to the lateral heat transfer. The DS sample prepared by this method can achieve finer columnar crystals growing toward the axis, a2/ y lamellae, and lower levels o f contamination with regard to Y2O3 particles and oxygen. These are beneficial to improve room temperature fracture toughness and tensile properties.