Nb含量对TiAl合金铸态组织的影响

Effect of Nb content on microstructure of as-cast TiAl alloy

利用金相显微镜(OM)、X射线衍射仪(XRD)和扫描电镜(SEM)及能谱分析(EDS)等测试方法研究Nb含量对铸造TiAl-xNb(x=1,3,5,7;原子分数,%)合金组织的影响。结果表明:Nb含量为1%时,TiAl-Nb合金铸锭组织主要为单相的γ组织;随Nb含量升高,合金组织主要为α2/γ层片组织;并在层片组织间存在2种偏析,分别是网状β相和γ相,合金的层片晶团平均尺寸逐渐增加,β相的体积分数逐渐升高;当合金中Nb的含量从1%增加到7%,层片晶团平均尺寸由89μm增加至190μm,β相的体积分数从1.9%增至12.9%;随合金中Nb含量增加,β相中Nb含量增加而Cr含量减少,γ相的偏析区域宽度变窄。

The effect of Nb content on the microstructure of as-cast TiAl-xNb （x=1,3,5,7; atom fraction,%） alloy was investigated by means of optical microscopy （OM）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS）. The results show that when the Nb content is 1%, the structure of as-cast TiAl-Nb is mainly singleγphase;with the increase of Nb content, the main structure of alloy isα2/γlamellar;there exist two kinds of segregations in lamellars, indicating to be webβphase andγphase, the average size of lamellar colony and the volume fraction ofβphase increase;with increasing Nb content from 1%to 7%, the average size of lamellar colony decreases from 89μm to 190μm, the area fraction ofβphase increases from 1.9%to 12.9%;with increasing Nb content in as-cast TiAl alloy, the Nb content in β phase increases while the Cr content in β phase decreases, the width of γ segregation decreases.