高Nb-TiAl合金α2→α等温相变中的组织演变

Microstructure evolution of Ti-45 Al-8. 5 Nb-( 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 of α_2→α is 1140 ～1209 ℃ and the growth curve of α phase is"S"shape during isothermal treating. The microstructure of this alloy is lamellar and it is consisted of α_2,γ and a little of βphase. β phase at the grain boundary gradually decreases with the holding time increasing and the size of γ phase generated along the grain boundary increases,however,the microhardness of alloy increases firstly and later decreases with the increase of holding time.

摘要:

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α_2→α相变温度区间为1 140～1 209℃;α_2→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α_2、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。

Abstract:

Microstructure evolution of Ti-45 Al-8. 5 Nb-( 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 of α_2→α is 1140 ～1209 ℃ and the growth curve of α phase is"S"shape during isothermal treating. The microstructure of this alloy is lamellar and it is consisted of α_2,γ and a little of βphase. β phase at the grain boundary gradually decreases with the holding time increasing and the size of γ phase generated along the grain boundary increases,however,the microhardness of alloy increases firstly and later decreases with the increase of holding time.