高温变形时 Al_(67)Mn_8Ti_(25) 的动态回复和动态再结晶

Dynamic Recovery and Dynamic Recrystallization of Al 67 Mn 8Ti 25 Compound during High Temperature Deformation

采用透射电子显微术研究了Ａｌ６７Ｍｎ８Ｔｉ２５金属间化合物高温拉伸变形后的显微组织．结果表明，该合金在１１７３Ｋ和８．３５×１０－５ｓ－１条件下的塑性变形过程是以动态回复为主，变形后晶粒内存在较高密度的位错、位错墙和位错网络；而在１１７３Ｋ及３．３４×１０－５ｓ－１条件下合金则发生了动态再结晶，变形后的组织为动态再结晶形成的新晶粒，晶粒内包含有稳定的亚晶界．Ａｌ６７Ｍｎ８Ｔｉ２５合金高温塑性变形是一典型的速率控制过程．由于该合金中的位错运动及与原子扩散有关的过程进行较为困难，故只有在足够高的温度和低的应变速率条件下才发生动态回复和动态再结晶，同时合金获得较高的拉伸塑性．

The deformation microstructure of Ll 2 structure Al 67 Mn 8Ti 25 compound after tension at high temperature was investigated by TEM. The results show that dynamic recovery occurs and there exist a high density of dislocations, dislocation walls and unstable networks within the grains after deformation at 1 173 K and a strain rate of 8.35×10 -5 s -1 . At 1 173 K and a strain rate of 3.34×10 -5 s -1 , dynamic recrystallization took place and the deformation microstructures were fine recrystallized grains with stable sub boundaries in the specimen. Owing to difficulties in the dislocation motion and the process concerned with atom diffusion, the dynamic recovery and dynamic recrystallization occur only at rather higher temperature and lower strain rates, and only under this condition can the appreciate tensile ductility be obtained for this compound.