高Nb-TiAl合金α2→α等温相变中的组织演变

Microstructure Evolution ofα2→αPhase Transformation in High Nb-TiAl Alloy under Isothermal Treatments

采用热膨胀法结合金相显微镜(OM)、X射线衍射仪(XRD)和显微硬度等测试手段,系统研究了固溶处理后Ti-45Al-8.5Nb-(W,B,Y)合金在等温过程中的显微组织演变规律。结果表明:高Nb-TiAl合金α2→α相变温度区间为1140~1209℃;α2→α等温相变过程中,α相的形成呈“S”形曲线,合金在等温过程中显微组织主要由α2、γ相和少量β相形成的片层结构组成,随保温时间的延长,晶界处存在的β相逐渐减少;沿晶界产生的细小等轴γ晶粒逐渐增大;显微硬度随保温时间延长呈先增大后减小的趋势。

Microstructure evolution of Ti-45Al-8.5Nb-(W,B,Y)alloy exposed to isothermal processing were investigated using dilatometry(DIL),optical microscopy(OM),X-ray diffraction(XRD)and microhardness tester.The results indicate that the transformation temperature ofα2→αis 1140~1209℃and the growth curve ofαphase is“S”shape during isothermal treating.The microstructure of this alloy is lamellar and it is consisted ofα2,γand a little ofβphase.βphase at the grain boundary gradually decreases with the holding time increasing and the size ofγphase generated along the grain boundary increases,however,the microhardness of alloy increases firstly and later decreases with the increase of holding time.