Nb合金化γ-TiAl的氧化热力学理论分析

THERMODYNAMIC ASPECTS OF OXIDATION FOR Nb ALLOYING γ-TiAl INTERMETALLIC COMPOUNDS

利用亚点阵的准亚规则溶体模型计算了Ｔｉ－ＡＬ－Ｎｂ三元系合金热力学活度，根据金属氧化反应用热力学计算了相应的 Ｔｉ／ＴｉＯ和 Ａｌ／Ａｌ２Ｏ３的氧平衡分压．讨论了 Ｎｂ合金化对γ－ＴｉＡｌ金属间化合物热力学活度和氧化反应的氧平衡分压的影响，计算的热力学活度与Ｋｎｕｄｓｅｎ池隙透法测量的规律相符． 由Ｎｂ合金化γ－ＴｉＡｌ的热力学活度以及氧化反应的氧平衡分压变化不能判定Ｔｉ－Ａｌ－Ｎｂ三元系合金生成氧化物的种类及其稳定性．

The thermodynamic activities in the Ti-Al-Nb ternary alloys were calculated using a two-sublattice quasi-subregular solution model, and the oxygen equilibrium pressures of Ti/TiO and Al/Al2O3 reactions were calculated from the free energy of the oxides formation. The effects of Nb alloying on the thermodynamic activities and oxygen equilibrium pressures of the γ-TiAl compounds during oxidation were evaluated. The calculated thermodynamic activities are consistent with those measured by the Knudsen cell mass spectrometer system. The formation of oxides and their stability are independent of the thermodynamic activities and oxygen equilibrium pressures in the Ti-Al-Nb ternary alloys. The change of the thermodynamic parameters is not enough to explore the mechanism of oxidation resistance for the Nb allying γ-TiAl intermetallic compounds.