铸造TiAl合金FFL组织形成动力学及机理

The Generating Kinetics and Mechanisms of the Cast TiAl Intermetallic Alloy FFL Microstructure

对铸造Ｔｉ－４６．５Ａｌ－２．５Ｖ－１．０Ｃｒ（ａｔ％）合金，试验研究了层片组织在等轴ＮＧ组织中形成的动力学规律，得出容易控制细小全层片（ＦＦＬ）组织形成动力学的热处理温度是略高于Ｔα的１３７０℃。发现在１３７０℃ＦＦＬ组织形成机理包括，在α相区温度原ＮＧ组织中的γ晶粒分解为γ／α。层片结构，冷却中形成不同取向的γ／α２层片团；和原α２晶粒升温时无序化为α相并长大，冷却中α相分解为α／γ层片结构，并转变为α２／γ层片团。

The tensile properties、fracture or creep resistance of the present TiAl intermetallic alloy microstructures exhibit an inverse relation. Developing the fine fully lamellar (FFL) microstructure is an effective way to balance these two kinds of mechanical properties. This paper conducts a series of the FFL's generating kinetics tests and microstructure analyses on the cast Ti-46. 5Al-2.5V-1Cr(at%) alloy. The heat treatment temperature at which the generating kinetics of the FFL microstructure is acceptably tolerant has been found to be slightly above the Ta And it's also revealed that the generating mechanisms involve the prior γ grains' decomposing to γ/a lamellar structures at 1370℃ then generating various γ/a2 lamellar colonies when cooling, and the prior a2 grains' transforming to disordered a at 1370℃ then decomposing to a/γ later a2/γ lamellar structures in the process of ccoling.