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研究了Nb含量对铸造高铝Ti Al合金(%,原子分数)Ti-48Al-x Nb-2.5V-1.0Cr(x=2,4,7,9),以下分别简称2Nb,4Nb,7Nb和9Nb合金)组织和室温拉伸性能的影响。组织观察发现:不同Nb含量合金宏观组织均为柱状晶组织,微观组织均为有取向层片组织。经X射线衍射(XRD)分析表明,不同Nb含量合金均由γ相、α_2相和少量的B2相组成,其中,γ相体积分数随Nb含量的增加而增多;α_2相体积分数随Nb含量的增加而减少;B2相含量由于含量较少无法定量,但从XRD谱及扫描电镜(SEM)背散射(BSE)图可定性得知,其含量随Nb含量的增加而显著增多。合金室温抗拉强度随Nb含量的增加而降低:由2Nb合金的648.2 MPa降为9Nb合金的613.8 MPa;但屈服强度却随Nb含量的增加而升高:由2Nb合金的561.1 MPa增为9Nb合金的613.5 MPa。合金室温延伸率随Nb含量的增加呈线性下降:由2Nb合金的延伸率1.2%,降为9Nb合金的0.3%。γ相的晶格常数c/a随Nb含量的增加而增大,这对合金的室温塑性有不利的影响。
The effects of Nb content on the microstructure of TiAl alloy (%, atomic fraction) Ti-48Al-xNb-2.5V-1.0Cr (x = 2, 4, 7 and 9) 9Nb alloy) microstructure and tensile properties at room temperature. Histological observation showed that the macrostructure of Nb alloy with different contents of Nb was columnar crystal structure, and the microstructure was oriented ply tissue. The results of X-ray diffraction (XRD) showed that the alloys with different Nb contents consist of γ phase, α_2 phase and a small amount of B2 phase. The volume fraction of γ phase increases with the increase of Nb content. The volume fraction of α_2 phase increases with the increase of Nb content But the content of B2 phase can not be quantified due to its small content. However, the X-ray diffraction (XRD) and scanning electron microscopy (SEM) backscatter (BSE) images show that the content of B2 phase increases with the increase of Nb content. The tensile strength at room temperature decreases with the increase of Nb content from 648.2 MPa for 2Nb alloy to 613.8 MPa for 9Nb alloy. However, the yield strength increases with the Nb content increasing from 561.1 MPa for 2Nb alloy to 9Nb alloy Of 613.5 MPa. The room temperature elongation of alloy decreases linearly with the increase of Nb content: from 1.2% elongation of 2Nb alloy to 0.3% of 9Nb alloy. The lattice constant c / a of γ phase increases with the increase of Nb content, which has an adverse effect on the room temperature plasticity of the alloy.