Ti-Al-Nb-W基合金高温变形过程中的组织演化

在Thermecmastor-Z动态热模拟试验机上对Ti-43Al-4Nb-1.4W和Ti-43Al-4Nb-1.4W-0.6B-0.2Y合金进行高温压缩变形实验(实验温度范围为1 050~1 150℃,应变速率范围为0.001~1 s 1),对其热变形组织进行显微分析,并利用热加工Z参数(Zener-Hollomon参数)综合描述变形温度及应变速率对材料热变形行为的影响。结果表明:2种合金在不同高温压缩变形条件下均发生不同程度的动态再结晶;随Z参数值的降低,β相逐渐由不规则形状转变为球形,且长大明显,同时,动态再结晶晶粒的体积含量也随之增加;Ti-43Al-4Nb-1.4W基合金的高温变形机制与Z参数值密切相关;在低Z值条件下,其主要变形机制为动态再结晶和β相的球化、长大;在高Z值条件下,其主要变形机制为片层的扭折、重新取向和局部动态再结晶;加入微量B和Y后,动态再结晶程度增大,这主要与颗粒诱发动态再结晶形核有关。

Microstructure evolution of Ti-Al-Nb-W alloy during hot deformation

The hot deformation behaviors of Ti-43Al-4Nb-1.4W and Ti-43Al-4Nb-1.4W-0.6B-0.2Y alloys have been studied in the temperature range of 1 050~1 150 ℃ and the strain rate range of 0.001~1 s 1 using hot compressing test on a thermecmastor-Z dynamic simulator.The microstructures of deformed specimens were observed,and the Zener-Hollomon(Z) parameters were introduced to demonstrate the effect of the temperature and strain rate on the deformation behavior of Ti-43Al-4Nb-1.4W based alloy.The results show that,for above mentioned alloys,dynamic recrystallization occurs under different deformation conditions.And the fraction of the dynamic recrystallization grains increases with decreasing Zener-Hollomon(Z) parameter.Meanwhile,the morphology of β phase gradually changes from irregular shape to globular along with decreasing Z parameter.The deformation mechanisms of Ti-43Al-4Nb-1.4W based alloys are also related to Z parameter.Under low Z conditions,dynamic recrystallization as well as globalization and growth of β phases are the main deformation mechanisms.While,under high Z conditions,the main deformation mechanisms are the kinking and reorientation and the dynamic recrystallization of the lamellar structures.After added B and Y,the fraction of the dynamic recrystallization becomes higher which can be mainly attributed to the acceleration of TiB2and Y2O3to the nucleation of dynamic recrystallization.