等温锻造对Ti－47Al—5（Cr＋V＋Mo＋Nb）合金组织的影响

Effect of Isothermal Forging on the Microstructure of Ti-47Al-5(Cr+V+Mo+Nb) Alloy

通过等温锻造方法对Ｔｉ－４７Ａｌ－５（Ｃ＋Ｖ＋Ｍｏ＋Ｎｂ）（ａｔ％）合金进行组织控制。研究发现，由于合金在凝固过程中存在两个包晶反应，导致枝晶间铝含量的分布极不平衡，从而使铸锭组织不均匀，含有大量的γ＋α２片层组织。在热加工中，片层组织在大变形量下发生剪切变形或严重弯曲。剪切变形组织沿平行于片层边界作用，使各片层团间产生大量再结晶晶粒并呈无序生长；而由于γ和α２取向关系发生畸变，γ和α２由片层形式趋向于等轴。本研究还对γ－ＴｉＡｌ合金再结晶机理进行了讨论。

Controlling microstructure of Ti-47 Al-5 (C r+V+Mo +Nb ) ally by means of isothermal forging has been studied. Results show that distribution of aluminium atoms in dendritic Structure is inhomgeneous because of the two peritectic reaction during cooling of γ-ToAl ingot, which results in a number of lamellar (γ+α2) structures. Shearing strain and heaVy bending in lamellar structure of γ-TiAl alloy can be caused by heavy deformation during hot working. The shearing strain, which is parallel to the boundaries of lamellar structure, can make lamellar structure produce a lot of dynamic recrystallized structures and the grains grow up irregularly. Because the orientation of γ and α2 grains of lamellar structure with heaVy bending is distorted, the γand α2 grains do not exist as lamellar structure, but as equiaxel one. Mechanism of dynamic recrystallization of γ-TiAl alloy is also studied.