| TiAl based alloys have excellent combination of properties, low density,high-temperature strength, high melting point, high elastic modulus, oxidation resistance, andcreep resistance, which can be widely applied in aerospace domains. However, the resource isgravely waste caused by recycling difficulty due to oxidizition. Our research team invented anew method----melt hydrogenation technique (MH). MH was used to study the severalaspects of TiAl alloys below.In this paper, the MH is used to Ti-47Al-2Cr-2Nb alloy to study the effect on removal ofimpurities, microstructures and mechanical property. At first, the refine effect of MH on theimpurities O in Ti-47Al-2Cr-2Nb alloy melt was investigated. It was clearly showed that MHhad perfect effect on deoxidation by the experimental data. The oxygen content declinedgradually with the partial pressure of hydrogen and the melting duration increasing.Deoxidation mechanism was analyzed by change of Gibbs free energy. It was foundthe reactions of hydrogen with oxygen in the melt surface would be the crucial part.Then, based on Miedema model, Sievert’s law and isothermal equations, oxygensolubility in Ti-47Al-2Cr-2Nb alloy was calculated. The relationship of oxygen solubility inthe alloy melt among partial pressure of hydrogen, water vapor and melt temperature wasestablished.After performing MH on Ti-47Al-2Cr-2Nb alloy its influence on solidification structureswas studied. The coarse columnar grains grew into much finer columnar plus equiaxedgrains. And in some grains the angle of secondary dendrite and primary dendrite was60. Forthe specimen with high content of oxygen,Al2O3Precipitates were found. Thehydrogen-induced refinement is related to hydrogen-promosed grain free, andhydrogen-enhanced constitutional supercooling. The effect of hydrogen on hot deformation ofTi-47Al-2Cr-2Nb alloy was carried out by a Gleeble hot simulator. Deformationtemperature, strain rate, hydrogen and oxygen content had influence on peakstress and flow stress. The deformation mechanism of Ti-47Al-2Cr-2Nb alloy is mainlydislocation slipping, also superdislocation and twinning. Hydrogen contribute to dislocationmovement, dynamic recrystallization nucleation and twinning. |
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