Ti-20Al-22Nb合金的凝固组织转变及力学行为

Transformation of Solidified Structure and Mechanical Behavior of Ti-20Al-22Nb Alloy

摘要:

采用熔模铸造方法制备了名义成分为Ti-20Al-22Nb(at%)的合金,分别对铸态、热等静压及退火态进行了显微组织及室温拉伸性能分析。结果显示,合金由β基体、针状α2相及少量O相组成的,铸态下为粗大的魏氏组织,由于非平衡凝固,原始晶粒内部组织转变不完全,组织中的疏松缺陷及组织不均匀导致合金低的塑性；经过α2+β/B2两相区热等静压消除了疏松缺陷,原始晶粒内部充分析出细小针状的α2相,组织均匀性提高,合金的拉伸延伸率由2%提高到5%；经过α2+/B2+O三相区退火热处理,过饱和β相向平衡态转变,通过包析转变β/B2+α2→O,在针状α2相周围形成环带状O相,合金的延伸率提高到11%。

Abstract:

Ti-20Al-22Nb (at%) alloys were prepared by investment casting. The microstructures and tensile properties at room temperature of as-cast, hot isostatic pressing and annealed alloys were analyzed. The results show that solidified alloy has course widmanstatten structure, which consists with β matrix, fine acicular α2 phase and a small amount of O phase. The phase transformation inside original β/B2 grain was incomplete owing to non-equilibrium solidification. The loose defect and inhomogeneity of microstructures causes low plasticity of the material. The porous defects are eliminated by hot isostatic pressing in the two-phase region ofα2+β/B2. , peritectoid reaction of β/B2+α2→O promotes the formation of ring O phase around strip α2 phase, and β phase path through a process of equilibrium state transportation. The elongation of the alloy increases from 2% to 5%. Increase to 11%.