Ti-22Al-25Nb合金剪切旋压过程中显微组织演化

通过剪切旋压试验,研究了旋压温度(910℃和1000℃)和减薄率(0、10%和30%)对Ti-22Al-25Nb合金显微组织的影响,探讨了旋压过程中的显微组织演化规律。结果表明:Ti-22Al-25Nb(原子数分数)合金旋压组织主要由α2相、B2相和O相组成,在旋压过程中,B2晶粒沿旋轮进给方向被拉长,且伴随有动态再结晶现象发生;温度主要影响Ti-22Al-25Nb合金中α2相与O相的尺寸和形貌,随着旋压温度的升高,O相片层逐渐变短并粗化,α2相趋向等轴化;变形量主要影响α2相体积分数与O相形貌,随着减薄率的增大,α2相体积分数逐渐减少,O相从片层状转变为短棒状。因此,Ti-22Al-25Nb合金剪切旋压过程中不仅发生晶粒变形与动态再结晶现象,更涉及复杂的相变行为,组织控制困难。

Microstructural Evolution for Ti-22Al-25Nb Alloy During Shear Spinning

The effect of spinning temperature (910℃ and 1000℃) and reduction ratio (0,10％,30％) during shear spinning on the microstructural evolution of Ti-22Al-25Nb alloy is investigated.The experimental results show that the microstructure of Ti-22Al-25Nb alloy consisted of α2 phase,B2 phase and O phase.During spinning process,B2 grains are elongated along the spinning direction.The equiaxed fine grains which distribute around the elongated grains are related to dynamic recrystallization.The spinning temperature can significantly affect the size and morphology of α2 phase and O phase.With the increasement of temperature,lamellar O phase become shorter and coarser,α2 phase tends to be equiaxed.Deformation affects the volume fraction of α2 phase and the morphology of O phase.Obviously,the volume fraction of α2 phase decreases and O phase transforms from lamellar to clubbed as the increasement of reduction ratio.Thus,not only the dynamic recrystallization and deformation of grains occur for Ti-22Al-25Nb alloy during shear spinning,but also involves the complex phase transition which is difficult to control.