燃烧合成TiAl合金结构转变动力学的端部淬火熄灭法分析

EndQuenching and Extinguishing Analysis of Microstructural Evolution Kinetics in the TiAl Alloy Synthesized by Combustion

摘要:

采用端部淬火熄灭法分析了蔓延工燃烧合成了Ｔｉ－５０ａｔ％Ａｌ合金中的组织结构转变动力学过程，发现合成反应从铝粉熔化处开始，合成反应表现为Ｔｉ＋Ａｌ→１／３ＴｉＡｌ３＋２／３Ｔｉ→ＴｉｘＡｌ＋（１－ｘ）Ｔｉ→ＴｉＡｌ等一系列过渡反应过程，这些反应的前期是可依赖液态反应物流动铺展进行质量传递的快速液－固型反应，可使试样温度迅速升高，为后续固－固型反应奠定良好扩展条件，由于扩散质量传递速度明显代于液相流

Abstract:

The kinetics of microstructural transformation has been analyzed using an endquenching and extinguishing method for a Ti50at%Al alloy synthesized by combustion. It is shown that from start of aluminum powder melting, a series of transition reactions takes place one after another as follows: Ti+Al1/3TiAl3+2/3TiTixAl+(1-x)TiTiAl. The liquidsolid reaction at the early stage may heat the sample quickly, which can create a good condition for later solidsolid reactions. Since masstransfer during solidstate diffusion is much slower than that within liquid reactants, the later solidsolid reactions slow and some Ti core is left in the alloy for rapid cooling. The aluminum contents of the boundary layers of the Ti cores are higher than those of central parts of the Ti cores, and the boundary layers transform into annular 2Ti3Al phase during cooling.