Ta对新β型γ-TiAl基合金板材组织与性能的影响

Effect of Ta on Microstructure and Hardness in βTitanium Aluminides Sheet

摘要:

本文以Ti-42.5Al-2Cr-0.2W与Ti-42.5Al-2Cr-0.2W-3Ta合金板材为研究对象，系统分析了Ta对两种合金的不同状态显微组织及硬度的影响规律与内在的机制变化。结果表明：加工状态下，未含Ta的组织中片层粗大且原始α晶粒较多；含Ta的组织片层细小均匀，再结晶晶粒数量多，原始α晶粒少。热处理状态下，含Ta的组织中片层球化趋势增加，B2相易分解为α2+γ。热处理时间延长，未含Ta的合金组织内的晶团长大速度更快。TEM组织中含Ta的合金板材组织中存在更多的β相以及少量的ω相，不含Ta的组织中β相少且无ω相。此外，硬度分析发现含有Ta的γ-TiAl合金板材硬度值低于不含Ta的合金板材，这与片层细小及β、ω相的数量有关。

Abstract:

Microstructure and hardness of Two β TiAl alloys, with nominal composition of Ti-42.5Al-2Cr-0.2W-3Ta and Ti-42.5Al-2Cr-0.2W (at.%), were investigated. Both as-rolling and heatreated alloys were examined by optical and scanning electron microscopy and transmission electron microscopy. As-rolling, the lamllar were coarse and the α grain enriched inTi-42.5Al-2Cr-0.2W alloy. Tantalum additions were effective in grain refinement, recrystal grains enriched and the α grain depleted in the microstructure. When the heatreatment temperature increased, the lamellar colonies globularizated more, metastable β phases decomposited as α2+γ.And the time increased, the lamella grain and the γ grain also increased rapidly and respectively in Ti-42.5Al-2Cr-0.2W alloy . The microstructure of the sheet with Ta contained more β phases than the sheet without Ta. Meanwhile, the ω phase precipitated in the alloy with Ta. Besides, the value of hardness for the alloy with Ta was lower than the alloy without Ta, for the Tantalum was effective in grain refinement, the number of β phases and ω phases was few in microstructure.